327 core topics
+ 11 prerequisite topics taught
as needed · approximately 95 hours of instruction
including spaced review
An adaptive diagnostic (up to
40 questions) places the student on the course's knowledge
graph - topics already known are credited, and instruction begins exactly
at the learning frontier. Every topic is taught with a worked-example
lesson and auto-graded practice; a topic is mastered at
75%+ and then maintained through spaced reviews on an
expanding schedule. Mixed checks follow every 6 lessons;
each unit ends with a 12-item quiz, and course-wide assessments appear at
25%, 50%, 75%, and 100% mastery. Prerequisite gaps below the course are detected and taught rather
than skipped, so completion certifies the whole tower, not just the top.
| Place Value & Comparing
[E] |
Each digit's position multiplies its value by ten. |
| Rounding & Estimation
[E] |
Look one digit to the right: 5 or more rounds up. |
| Multi-Digit Multiplication
[E] |
Split by place value, multiply each part, add. |
| Long Division
[M] |
Divide, multiply, subtract, bring down - repeat. |
| Time & Elapsed Time
[E] |
Count up to the next hour, then keep going. |
| Money Problems
[E] |
Money is decimals with two places - line up the point. |
| Units & Measurement
[E] |
Bigger unit → multiply; smaller unit → divide. |
| Perimeter & Area of Rectangles
[E] |
Perimeter walks around; area covers. |
| Reading Graphs & Tables
[E] |
Read the values first; the math is the easy part. |
| Multi-Step Word Problems
[M] |
One sentence at a time: what do I know, what changes, what's asked? |
| GCF & LCM
[E] |
Greatest common factor and least common multiple. |
| Prime Factorization
[E] |
Every whole number is a unique product of primes. |
| Absolute Value & Distance
[E] |
Absolute value is distance from zero. |
| Unit Rates
[E] |
Per-one comparisons: dollars per item, miles per hour. |
| Ratio Tables & Equivalent Ratios
[E] |
Scaling both parts of a ratio keeps it equivalent. |
| Area: Triangles & Trapezoids
[E] |
Half of base times height - and its trapezoid cousin. |
| Area of Composite Figures
[E] |
Split odd shapes into rectangles and triangles. |
| Volume: Rectangular Prisms
[E] |
Length × width × height, fractional edges included. |
| Surface Area & Nets
[E] |
Unfold the box: surface area is the area of its net. |
| Mean, Median & Range
[E] |
Three ways to summarize a data set with one number. |
| Reading Data Displays
[E] |
Pulling answers out of dot plots, tables, and bar graphs. |
| Probability Basics
[E] |
Favorable outcomes over total outcomes. |
| Rewriting with Common Denominators
[E] |
Before unlike fractions can meet, rename them with the same-size pieces. |
| Adding Unlike Fractions in Context
[M] |
Rename to a common denominator, then add the numerators - story or not. |
| Subtracting Unlike Fractions in Context
[M] |
How much more, how much left - common denominator first, then subtract tops. |
| Estimating Sums with Benchmark Fractions
[M] |
Round each fraction to 0, 1/2, or 1 before computing - the estimate polices the answer. |
| Fraction × Fraction with Area Models
[M] |
Columns for one fraction, rows for the other - the overlap is the product. |
| Fraction of an Amount
[M] |
“Of” means multiply: divide by the bottom, multiply by the top. |
| Multiplication as Scaling
[M] |
Compare the factor to 1 - that alone says whether the product grows or shrinks. |
| Dividing a Unit Fraction by a Whole Number
[M] |
Splitting 1/b into n equal shares makes pieces n times smaller: 1/(b × n). |
| Dividing a Whole by a Unit Fraction
[M] |
n ÷ 1/b asks how many 1/b-size pieces fit in n - every whole holds b of them. |
| Mixed Numbers with Unlike Denominators
[M] |
Handle wholes and parts separately - but give the parts a common denominator first. |
| Multiplying Mixed Numbers
[M] |
Convert each mixed number to an improper fraction, then multiply straight across. |
| Multi-Step Fraction Word Problems
[H] |
Chain the moves: combine the fractions first, then compare to the whole. |
| Nested Grouping Symbols
[E] |
Work from the innermost parentheses outward. |
| Comparing Expressions
[E] |
Parentheses can make the same numbers give a bigger or smaller value. |
| Writing Expressions from Words
[E] |
Turn a phrase into symbols - parentheses show what happens first. |
| Interpreting Expressions
[E] |
See what an expression says without grinding out the arithmetic. |
| Rules & Input-Output Tables
[E] |
Apply a two-step rule forward - or undo it backward. |
| Generating Number Patterns
[E] |
Follow the rule step by step to grow the pattern. |
| Comparing Two Patterns
[M] |
Line up matching terms and see how the two rules relate. |
| Ordered Pairs from Patterns
[M] |
Pair matching terms as (x, y) points ready to plot. |
| Reading Points in Real-World Graphs
[E] |
A point (x, y) tells a story: x of one thing, y of another. |
| Classifying Triangles
[E] |
Name triangles by their sides or by their angles. |
| The Quadrilateral Hierarchy
[M] |
Categories nest: a square is a rectangle is a parallelogram. |
| Multi-Step Conversion Problems
[M] |
Convert to one unit first, then finish the problem. |
| Opposites in Context
[E] |
Every number has a mirror twin on the other side of zero. |
| Absolute Value in Context
[E] |
Absolute value answers 'how far from zero?' - order answers 'which is greater?' |
| Comparing & Ordering Rational Numbers
[E] |
Smaller means farther left on the number line - even below zero. |
| Rational Numbers on the Number Line
[E] |
Fractions and decimals claim exact spots between the integers. |
| Plotting in All Four Quadrants
[E] |
Negative coordinates open up the other three quadrants. |
| Reflections Across the Axes
[E] |
Reflecting a point just flips the sign of one coordinate. |
| Distances on the Coordinate Plane
[M] |
Same x or same y: subtract and take the absolute value. |
| Rectangles on the Coordinate Plane
[M] |
Coordinates give the side lengths; perimeter and area follow. |
| Dividing Fractions: Word Problems
[M] |
'How many of this size fit?' is a division by a fraction. |
| Decimal Operations in Context
[E] |
Money problems are decimal arithmetic with two places, always. |
| Dividing Decimals in Context
[M] |
Slide both decimal points until the divisor is whole, then divide. |
| Percent of a Quantity: Parts & Wholes
[M] |
Percent problems run in three directions: find the part, the percent, or the whole. |
| The Volume Formula V = l × w × h
[E] |
Multiply the three edge lengths - no more counting cubes one by one. |
| Base Area × Height: Thinking in Layers
[E] |
A prism is a stack of identical layers, so volume is base area times height. |
| Volume Word Problems
[M] |
Spot the three dimensions hiding in a story, then multiply them. |
| Finding a Missing Dimension
[M] |
Divide the volume by the dimensions you know to uncover the one you don't. |
| Comparing Volumes
[E] |
Compute each volume, then subtract to see how far apart they are. |
| Volume of Composite Solids
[M] |
Split an L- or step-shaped solid into two prisms and add their volumes. |
| Volume by Subtraction
[M] |
When a piece is carved away, find the whole, find the hole, and subtract. |
| Packing Problems: How Many Fit?
[M] |
Count how many fit along each edge, then multiply the three counts. |
| Liquid Volume: Liters & Milliliters
[E] |
Convert between liters and milliliters to solve pouring and filling stories. |
| Mass Word Problems: Grams & Kilograms
[E] |
Turn kilograms into grams before adding, subtracting, or scaling masses. |
| Cubic Centimeters Meet Milliliters
[M] |
One cubic centimeter holds exactly one milliliter - volume becomes capacity. |
| Multi-Step Measurement Problems
[H] |
Chain a volume computation with a unit conversion to finish a real task. |
| Adding Up the Shopping Cart
[M] |
Multiply each price by its count, then add the lines like a receipt. |
| Unit Prices
[M] |
Divide the total by the count to find the price of just one. |
| Making Change
[M] |
Total the purchase first, then subtract it from what was handed over. |
| Budgets: Spending & Saving
[M] |
Track what goes out against what you started with - and what still fits. |
| Two-Step Whole-Number Problems
[M] |
Do the sentences in order: build the total first, then adjust it. |
| Equal Shares or Equal Groups?
[E] |
The same division answers two different questions - know which one you asked. |
| What the Remainder Means
[M] |
Round up, drop, or report the leftover - the story decides, not the arithmetic. |
| Recipe Problems: Add, Then Multiply
[M] |
Combine the fraction amounts for one batch, then scale up by the number of batches. |
| Fraction of a Group, Then One More Step
[M] |
Find the fraction of the group first - then answer what the story actually asks. |
| Mixing Decimals & Fractions
[H] |
Friendly numbers let fractions and decimals share one problem - take the fraction first. |
| Choosing the Operation
[M] |
Match the story's action to the right operation before touching the numbers. |
| Multi-Step Problem Marathon
[H] |
Three or more moves in one story - plan the steps before computing any of them. |
| Writing Addition & Subtraction Equations
[E] |
Turn a join-or-separate story into a one-step equation. |
| Writing Multiplication & Division Equations
[E] |
Equal-groups and fair-share stories become px = q or x ÷ p = q. |
| Solving Add & Subtract Equations in Context
[E] |
Undo one addition or subtraction to answer the story's question. |
| Solving Multiply & Divide Equations in Context
[E] |
Undo one multiplication or division to find the missing amount. |
| Is It a Solution?
[E] |
Substitute a value for the variable and see if both sides agree. |
| Money Equations
[M] |
One-step equations where the amounts are dollars and cents. |
| Evaluating Expressions in Context
[E] |
Substitute a number for the variable and follow the order of operations. |
| Dependent & Independent Variables
[E] |
Which quantity drives the relationship, and which one responds? |
| Using Two-Variable Equations
[E] |
Feed the independent variable into a rule to get the dependent one. |
| Writing Inequalities from Constraints
[E] |
Translate 'at least', 'more than', 'at most', 'fewer than' into symbols. |
| Graphing Inequalities on a Number Line
[E] |
Open or closed circle, shaded left or right - read and draw both ways. |
| Boundary Values of an Inequality
[E] |
Find the smallest or greatest whole number an inequality allows. |
| Equivalent Ratios in Context
[E] |
Scale both parts of a ratio by the same number to keep it equivalent. |
| Solving Problems with Ratio Tables
[M] |
Extend a ratio table by scaling a known row up or down. |
| Unit Rate as a Tool
[M] |
Divide to a per-one rate, then multiply back up to answer. |
| Unit Pricing & the Better Buy
[M] |
Reduce each option to price per unit, then the smaller one wins. |
| Finding a Part or the Whole from a Ratio
[M] |
One share of the ratio unlocks every part and the total. |
| Percent as a Rate per 100
[E] |
A percent is just a ratio scaled to a denominator of 100. |
| Finding a Percent of a Number
[M] |
Percent of a number = (percent ÷ 100) × the number. |
| Recognizing a Statistical Question
[E] |
A statistical question anticipates variety in its answers. |
| Mean, Median & Mode
[M] |
Three single-number summaries of the 'center' of a data set. |
| The Mean as a Fair Share & Balance Point
[M] |
The mean is what everyone gets when totals are shared out evenly. |
| Range: Measuring Spread
[E] |
Range is the distance from the smallest value to the largest. |
| Interquartile Range
[M] |
The IQR is the spread of the middle half of the data. |
| Describing the Shape of a Distribution
[E] |
Read a distribution's shape: symmetric, skewed, or uniform. |
| Dividing Fractions by Fractions
[M] |
Dividing by a fraction means multiplying by its reciprocal. |
| Whole-Number Exponents
[M] |
An exponent counts how many times the base is used as a factor. |
| Order of Operations with Exponents
[M] |
Exponents come before multiplication, which comes before addition. |
| Writing Algebraic Expressions
[M] |
Turn each phrase into an operation, watching the order words imply. |
| Combining Like Terms
[M] |
Add the coefficients of the x-terms; add the plain numbers separately. |
| The Distributive Property
[M] |
Multiply the outside factor by each term inside the parentheses. |
| Factoring Out the Greatest Common Factor
[M] |
Pull the largest shared factor to the front of the parentheses. |
| Identifying Equivalent Expressions
[M] |
Two expressions are equivalent if they agree for every value of x. |
| Volume with Fractional Edge Lengths
[M] |
Volume is length × width × height, even when the edges are fractions. |
| Converting Units with Ratios
[M] |
A conversion is a rate: multiply by how many small units fill one big one. |
| Mean Absolute Deviation
[M] |
MAD is the average distance of the data values from their mean. |
| Choosing the Better Measure of Center
[M] |
Use the median when an outlier would drag the mean; otherwise the mean. |
| Mean from a Frequency Table
[M] |
Multiply each value by its frequency, add, then divide by the count. |
| Reading a Box Plot
[M] |
The box marks Q1, median, and Q3; the whiskers reach the extremes. |
| Reasoning on a Double Number Line
[M] |
Scale both rows of the double number line by the same factor. |
| Unit Rates with Fractions
[H] |
Divide a fraction distance by a fraction time to get a per-one rate. |
| Working with Fractional Rates
[H] |
Multiply a per-one fraction rate up, or divide a total back down. |
| Setting Up Percent Equations
[H] |
Every percent problem is (percent as a decimal) × whole = part. |
| Solving Percent Problems with Equations
[H] |
Undo the multiplication in a percent equation to find the unknown. |
| Multi-Step Percent Problems
[H] |
Percents of the same whole add to 100, so the leftover group is 100 minus the rest. |
| LCM Word Problems
[H] |
Repeating events line up again at the least common multiple. |
| GCF Word Problems
[H] |
The greatest number of identical groups is the GCF of the counts. |
| GCF or LCM? Choosing the Tool
[H] |
Splitting into groups points to GCF; waiting for events to line up points to LCM. |
| Rewriting a Sum with the GCF
[H] |
Pull the GCF out of both addends: a + b = GCF x (sum of what is left). |
| Ordering Signed Numbers in Context
[H] |
Least means farthest left on the number line, not smallest digits. |
| Comparing Values and Absolute Values
[H] |
A number can be smaller in value yet larger in absolute value. |
| Grid Distances: Walking the Blocks
[H] |
Along the streets, distance is the across-change plus the up-change. |
| Right Triangles on the Coordinate Plane
[H] |
Coordinate differences give the legs; the area is half their product. |
| Distances Created by Reflections
[H] |
A point and its axis reflection sit twice the coordinate's distance apart. |
| Matching Nets to Solids
[M] |
Count and name a net's shapes to see which solid it folds into. |
| Surface Area of a Triangular Prism
[H] |
Two triangle ends plus three rectangles, one for each triangle side. |
| Surface Area Problems in Context
[H] |
Real surface-area problems drop faces or add a cost step. |
| Reading a Histogram
[H] |
Each bar counts the values falling in one interval of equal width. |
| Interpreting a Histogram
[H] |
Use interval counts to find the mode interval, percents, and the median's home. |
| Finding the Equation Behind a Table
[H] |
Test a candidate rule against every row - one row is never enough. |
| Extending a Two-Variable Table
[H] |
Recover the rule from the filled rows, then apply it to the new row. |
| Testing Solutions of an Inequality
[H] |
Substitute the value and check the comparison, watching the boundary. |
| Inequalities Below Zero
[H] |
Below zero, 'colder' and 'lower' move AWAY from zero on the number line. |
| Missing Exponents & Bases
[H] |
Work a power backward: keep multiplying the base until the target appears. |
| Comparing Powers
[H] |
Evaluate each power before comparing - a bigger base does not always win. |
| Edges from Areas and Volumes
[H] |
Undo s squared or s cubed by asking which number was multiplied by itself. |
| Powers of Ten
[M] |
10 to the k is a 1 followed by k zeros; multiplying appends the zeros. |
| Comparing Rates
[H] |
Convert each traveler to a per-one rate, then compare the rates. |
| Percents from Benchmarks
[H] |
Snap a percent to 10%, 5%, and 1% chunks and add the pieces. |
| Polygon Areas by Decomposition
[H] |
Cut a grid polygon into rectangles and right triangles, then add or subtract. |
| Multi-Step Unit Conversions
[H] |
Chain the conversion rates one hop at a time, then finish the question. |
| Volume Stories with Fractional Edges
[H] |
Use V = lwh forward for filling, backward for a missing edge, and count small cubes by volume. |
| Zero Pairs: Changes that Cancel
[M] |
A quantity and its opposite add to zero, so spot the pair that cancels first. |
| Exponents and Parentheses
[H] |
Parentheses decide what gets raised: the whole group, or just one base. |
| Multi-Step Ratio Word Problems
[H] |
Find the multiplier that scales the ratio, then read off any part. |
| Ratio Tables with a Missing Entry
[H] |
Every row shares one ratio; scale a full row to fill the blank. |
| Splitting a Total by a Ratio
[H] |
Add the ratio parts, divide the total into that many shares, hand them out. |
| Three-Term Ratios
[H] |
A three-part ratio scales exactly like a two-part one: one multiplier. |
| Part-to-Part and Part-to-Whole
[H] |
A part-to-part ratio a : b hides a part-to-whole fraction a / (a + b). |
| Ratios in Simplest Form
[H] |
Divide both terms by their greatest common factor to reach lowest terms. |
| Equivalent Ratios on a Double Number Line
[H] |
Whatever factor moves one row of a double number line, moves the other. |
| Which Ratio Is Stronger?
[H] |
Give both ratios a common term, or compare their unit rates, then decide. |
| Multi-Step Unit-Rate Problems
[H] |
Reduce to a per-one rate, then multiply by whatever amount is asked. |
| Comparing Unit Rates
[H] |
Turn each into a per-one rate; the larger per-one value is faster. |
| From a Unit Rate to a Big Total
[H] |
Multiply the per-one rate by the total count to scale all the way up. |
| Filling a Rate Table
[H] |
Find the constant per-one rate from a full row, then extend it. |
| Best Value Among Three Sizes
[H] |
Divide price by quantity for each; the smallest per-item price wins. |
| Distance = Speed x Time
[H] |
At a constant speed, distance is speed multiplied by time. |
| Time = Distance / Speed
[H] |
To find the time, divide the distance by the constant speed. |
| Speed = Distance / Time
[H] |
Speed is the distance covered divided by the time it took. |
| Multi-Leg Trips at Constant Speed
[H] |
Find each leg's distance with speed x time, then add the legs. |
| Comparing Two Travelers
[H] |
Find each traveler's distance, then subtract (or add) as the story asks. |
| Percent of a Quantity
[H] |
Percent of a number = (percent / 100) x the number. |
| Finding the Whole from a Part
[H] |
If a part is p% of the whole, the whole is the part divided by p/100. |
| What Percent Is This?
[H] |
Percent = (part / whole) x 100. |
| Percent Remaining
[H] |
The listed percents plus the leftover make a full 100 percent. |
| Sale Price after a Discount
[H] |
A p% discount leaves (100 - p)% of the price; multiply to get the sale. |
| Adding Sales Tax
[H] |
Tax is a percent of the price; the total is price plus that tax. |
| Figuring a Tip
[H] |
A tip is a percent of the bill; add it on, then split if needed. |
| Percent Increase in Context
[H] |
Increase = p% of the start; the new amount is start plus that increase. |
| Percent Decrease in Context
[H] |
Decrease = p% of the start; the new amount is start minus that decrease. |
| Markup and Selling Price
[H] |
Markup is a percent of the cost added on to set the selling price. |
| Discount, Then Tax
[H] |
Take the discount first, then charge tax on the discounted price. |
| Scaling a Recipe Up
[H] |
Find how many times bigger the batch is, then scale every ingredient. |
| Scaling a Recipe Down
[H] |
Making a fraction of a recipe multiplies every ingredient by that fraction. |
| A Missing Ingredient by Ratio
[H] |
Keep the recipe's ratio: scale the known ingredient to find the other. |
| Map Scale: Real Distance
[H] |
Multiply the map length by how many real units one map unit stands for. |
| Map Scale: Distance on the Map
[H] |
To go from real distance back to the map, divide by the scale. |
| Converting Length by Ratio
[H] |
A conversion is a rate: multiply to go to smaller units, divide to go up. |
| Converting Capacity and Weight
[H] |
Use the per-one conversion rate; multiply going down, divide going up. |
| Two-Step Unit Conversions
[H] |
Convert one step at a time: big to middle, then middle to small. |
| Converting the Units in a Rate
[H] |
Change a rate's time unit by multiplying or dividing by the conversion. |
| Servings from What Is Left
[H] |
Take away what is used first, then divide the rest by one serving. |
| Finishing the Leftover Piece
[H] |
Divide to find the leftover, then subtract it from one whole piece. |
| Unit Price from a Fractional Weight
[H] |
Divide the cost by the fractional weight to get the price per pound. |
| Comparing Servings from Two Pots
[H] |
Divide each pot by its own bowl size, then subtract the two counts. |
| A Missing Length from an Area
[H] |
Area equals length times width, so length is area divided by width. |
| Identical Bags with Nothing Left Over
[H] |
The most equal groups with no remainder is the GCF of the two counts. |
| When Two Schedules Line Up
[H] |
Two repeating events coincide again after the LCM of their periods. |
| Tiling a Floor with the Largest Square
[H] |
The largest square tile that fits with no cuts has side equal to the GCF. |
| Matching Packages Evenly
[H] |
The smallest equal total is the LCM of the two pack sizes. |
| Temperature Spread Across Cities
[H] |
Order the signed values, then subtract the lowest from the highest. |
| Vertical Distance with Signed Heights
[H] |
Distance is the absolute value of the difference of the two elevations. |
| How Deep Is the Deepest Debt?
[H] |
Distance from zero is absolute value; compare the sizes, not the signs. |
| Counting Values Past a Threshold
[H] |
A number is less than the cutoff if it lies to its left on the line. |
| Farthest from Zero
[H] |
Farthest from zero means largest absolute value, sign aside. |
| Rectangle from Two Corners
[H] |
A side length is the absolute difference of the matching coordinates. |
| Total Distance of a Grid Walk
[H] |
Each straight leg is an absolute difference; add the legs for the total. |
| Sizing a Rectangle from Three Corners
[H] |
Two corners share a coordinate; their gaps give the two side lengths. |
| Comparing Two Segment Lengths
[H] |
Measure each axis-aligned segment, then subtract the two lengths. |
| Grouping Symbols and a Power
[H] |
Do the parentheses, then the power, then multiply, then add or subtract. |
| Powers, Multiplication, and Division Together
[H] |
After the power, multiply and divide left to right before adding. |
| Evaluating Over a Fraction Bar
[H] |
Finish the whole grouped top, including the power, before dividing. |
| Squares and Cubes in Area and Volume
[H] |
A square's area is the side squared; a cube's volume is the edge cubed. |
| Order of Operations in a Story
[H] |
Translate the words to k times a square, minus what is removed. |
| Perimeter as an Expression
[H] |
Add all the side expressions, then combine the x-terms and the numbers. |
| Combining Like Terms in Two Variables
[H] |
Group the x-terms, the y-terms, and the plain numbers separately. |
| Writing Expressions with Parentheses
[H] |
When a whole sum or difference is acted on, wrap it in parentheses. |
| Write It, Then Evaluate It
[H] |
Turn the words into an expression, then substitute the given number. |
| Modeling a Cost with an Expression
[H] |
A per-unit charge multiplies the variable; a one-time fee is added once. |
| Distributing Over Three Terms
[H] |
The outside factor multiplies every term inside, one by one. |
| Distribute, Then Combine
[H] |
First distribute each factor, then collect like terms into one. |
| Factoring the GCF from Three Terms
[H] |
Pull the largest number that divides all three terms to the front. |
| Distributive Property for Mental Math
[H] |
Split a number into friendly parts, multiply each, then add. |
| Two-Step Cost Equations
[H] |
Subtract the one-time fee first, then divide by the per-unit rate. |
| Two-Step Savings Equations
[H] |
Subtract what is already saved, then divide by the weekly amount. |
| Budget Inequalities: The Most You Can Buy
[H] |
Spend the fee first, then see how many whole items the rest buys. |
| Goal Inequalities: The Fewest You Need
[H] |
Find how much more is needed, divide, then round up to a whole step. |
| A Fraction of the Whole Is Known
[H] |
A fraction of the whole equals the part, so divide the part by the fraction. |
| The Attribute a Question Measures
[H] |
A statistical question measures one attribute that varies across a group. |
| The Population a Question Studies
[H] |
The population is the whole group of individuals the data describe. |
| Leveling Data to a Fair Share
[H] |
Redistributing data to an equal amount produces the mean. |
| Recovering a Missing Value from the Mean
[H] |
The values must total mean times count; subtract to find a missing one. |
| The Score Needed to Reach a Target Mean
[H] |
The needed value is the target total minus the sum already earned. |
| How the Mean Shifts When a Value Is Added
[H] |
Rebuild the total with the new value, then divide by the new count. |
| Combining the Means of Two Groups
[H] |
Add both groups' totals, then divide by the combined count. |
| The Balance Point and a Missing Value
[H] |
Total distance below the mean must equal total distance above it. |
| The Median of an Even Number of Values
[H] |
With an even count the median is the mean of the two middle values. |
| The Median from a Dot Plot
[H] |
Count dots inward from both ends to the middle position of the data. |
| One Mode, Two Modes, or None
[H] |
The mode is the most frequent value; ties give two modes, all-different none. |
| The Mode from a Dot Plot
[H] |
The mode is the value with the tallest stack of dots. |
| A Missing Value from the Range
[H] |
Range is maximum minus minimum; add the range to the minimum to recover a top value. |
| The Quartiles of a Data Set
[H] |
Q1 is the median of the lower half; Q3 is the median of the upper half. |
| The Five-Number Summary
[H] |
The summary lists minimum, Q1, median, Q3, and maximum in order. |
| The IQR from a Raw Data List
[H] |
The IQR is Q3 minus Q1, the spread of the middle half of the data. |
| Choosing a Resistant Measure of Spread
[H] |
The IQR ignores the extremes, so an outlier barely moves it. |
| Counting Values in a Dot Plot
[H] |
Add the dots on the side of the threshold the question asks about. |
| The Mean from a Dot Plot
[H] |
Add every value (each dot counts once) and divide by the number of dots. |
| The Range from a Dot Plot
[H] |
Subtract the smallest value with a dot from the largest value with a dot. |
| The Shape of a Dot Plot
[H] |
Read symmetry, skew, or uniformity from where the dots pile up. |
| The MAD from a Dot Plot
[H] |
Average the distances of the dots from the mean. |
| Combining Two Intervals of a Histogram
[H] |
Add the frequencies (bar heights) of the two named intervals. |
| Counting Below a Boundary in a Histogram
[H] |
Add the frequencies of every interval that lies below the boundary. |
| Locating the Median in a Histogram
[H] |
Add frequencies from the left until you pass the middle data position. |
| The Total Count in a Histogram
[H] |
The total number of values is the sum of every bar's frequency. |
| Relative Frequency of an Interval
[H] |
Relative frequency is an interval's count divided by the total count. |
| The Percent of Data in a Box-Plot Region
[H] |
Quartiles cut the data into four groups of about 25% each. |
| Counting Values in a Box-Plot Region
[H] |
Multiply the total count by the fraction of data the region holds. |
| Comparing Two Box Plots
[H] |
Compute each plot's median, IQR, or range, then compare the numbers. |
| The Most Spread-Out Quarter of a Box Plot
[H] |
The longest section covers the quarter of data with the widest spread. |
| The Length of a Whisker
[H] |
A whisker's length is the distance from a quartile to that extreme. |
| Removing an Outlier and Recomputing the Mean
[H] |
Drop the far-off value, then average the values that remain. |
| Outliers: Mean versus Median
[H] |
The mean uses every value, so an outlier moves it more than the median. |
| Skew from the Mean-Median Gap
[H] |
The mean is pulled toward the tail, so mean above median means right skew. |
| Naming Features of a Distribution
[H] |
Clusters, gaps, peaks, and outliers name where data gather or stand apart. |
| Pairing a Center with the Right Spread
[H] |
Median goes with IQR for skewed data; mean goes with MAD for symmetric data. |
| Reading Spread from the MAD
[H] |
A larger MAD means the values sit farther from the mean on average. |
| Area of a Parallelogram
[H] |
A parallelogram's area is base times its perpendicular height. |
| A Missing Dimension of a Parallelogram
[H] |
Divide the area by the known dimension to recover the other one. |
| Base Times Height, Not the Slant Side
[H] |
Area uses the perpendicular height, never the length of the slanted side. |
| A Missing Base or Height of a Triangle
[H] |
From area = half base times height, double the area then divide. |
| Area of a Triangle with Fractional Dimensions
[H] |
The half-base-times-height rule holds when the lengths are fractions. |
| Area of a Trapezoid
[H] |
Average the two parallel bases, then multiply by the height. |
| A Missing Base of a Trapezoid
[H] |
Undo the trapezoid formula: from the area, back out the unknown base. |
| Trapezoid Area with Fractional Bases
[H] |
Add the fractional bases, halve the sum, then multiply by the height. |
| Choosing the Right Lengths for a Triangle's Area
[H] |
Area is one half the base times the perpendicular height to that base. |
| Composite Area: a Rectangle Plus a Triangle
[H] |
Decompose into a rectangle and a triangle, find each area, then add. |
| Area of a Border or Frame
[H] |
Subtract the inner opening's area from the outer rectangle's area. |
| Area of an L-Shaped Region
[H] |
Split the L into two non-overlapping rectangles and add their areas. |
| A Rectangle with a Triangle Removed
[H] |
Subtract the cut triangle's area from the whole rectangle's area. |
| Area of a Three-Rectangle Staircase
[H] |
Find the area of each step rectangle, then add all three together. |
| Perimeter of a Rectangle on the Plane
[H] |
Find each side length by subtracting coordinates, then add all sides. |
| Perimeter of a Polygon on the Plane
[H] |
Add the length of every side, each found from a coordinate difference. |
| Area of a Parallelogram on the Plane
[H] |
Read the horizontal base and the vertical height from the coordinates. |
| Area of a Trapezoid on the Plane
[H] |
The bases are the two horizontal sides; the height is their vertical gap. |
| Area on a Grid, Then a Cost
[H] |
Find the rectangle's area from its vertices, then multiply by the price. |
| Surface Area of a Cube
[H] |
A cube has six identical square faces, so its surface area is 6 s squared. |
| Surface Area of a Rectangular Prism from a Net
[H] |
Add the areas of the three pairs of faces: 2lw + 2lh + 2wh. |
| Total Area of a Net
[H] |
The net's area is the sum of the areas of all of its rectangles. |
| Surface Area of a Square Pyramid from a Net
[H] |
Add the square base to four triangular faces: s squared plus 4 half s l. |
| Matching the Faces in a Net
[H] |
Each face of a box is a rectangle made from two of the three edge lengths. |
| Faces, Edges, and Vertices of Prisms and Pyramids
[H] |
Count a solid's faces, edges, and vertices from the shape of its base. |
| Volume with Three Fractional Edges
[H] |
Volume is length times width times height, even for three fractions. |
| Volume with Mixed-Number Edges
[H] |
Rewrite mixed-number edges as improper fractions, then multiply. |
| Counting Unit-Fraction Cubes in a Prism
[H] |
Count how many unit-fraction cubes fit along each edge, then multiply. |
| A Missing Edge from the Volume
[H] |
Divide the volume by the product of the two known edges. |
| Comparing the Volumes of Two Prisms
[H] |
Compute both volumes as exact products, then compare the two numbers. |
| Carpeting a Room: Area Then Cost
[H] |
Find the floor area, then multiply by the cost per square foot. |
| Painting the Walls Around a Door
[H] |
Add the four wall areas, then subtract the door opening. |
| Packing Boxes into a Crate
[H] |
Count how many boxes fit along each edge, then multiply the three counts. |
| Filling a Tank to a Given Depth
[H] |
The water forms a prism: base times the water depth, not the full height. |
| Tiling a Floor: Counting Tiles and Cost
[H] |
Count tiles along each side, multiply for the total, then times the price. |
| Fencing a Garden: Perimeter Then Cost
[H] |
Find the perimeter for the fence length, then multiply by the price. |