298 core topics
+ 3 prerequisite topics taught
as needed · approximately 88 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.
| Ten Times the Place
[E] |
Each step left in a number makes a digit worth ten times more. |
| Comparing Numbers to 1,000,000
[E] |
Compare big numbers digit by digit from the left. |
| Big-Number Word Problems
[M] |
Add and subtract six-digit numbers inside real stories. |
| Factors & Factor Pairs
[E] |
Factors come in pairs that multiply to make the number. |
| Multiples
[E] |
The multiples of a number are its skip-counting list. |
| Prime or Composite?
[M] |
A prime has exactly two factors: 1 and itself. |
| Times as Many
[E] |
“3 times as many” means multiply - or divide to go backwards. |
| More Than vs. Times as Many
[M] |
“3 more” adds, “3 times as many” multiplies - don't mix them up. |
| What the Remainder Means
[M] |
The story, not the arithmetic, decides what to do with a remainder. |
| Division Stories with Remainders
[M] |
Divide, then round up, drop, or report the leftover - as the story asks. |
| Follow the Pattern Rule
[E] |
Apply a rule again and again - the first term counts as step one. |
| Find the Pattern's Rule
[M] |
Compare neighboring terms to uncover the rule, then test it everywhere. |
| Fractions from Equal Parts
[E] |
The bottom counts the equal parts; the top counts the parts you take. |
| Seeing Equivalent Fractions
[E] |
Cutting every part into k smaller pieces changes the name, not the amount. |
| Decomposing Fractions
[E] |
Every fraction is a stack of unit-fraction pieces you can split apart. |
| Comparing Fractions with Benchmarks
[M] |
Judge each fraction against 1/2 before reaching for common denominators. |
| Adding Mixed Numbers (Like Denominators)
[M] |
Add the wholes, add the parts, then trade a full set of parts for a whole. |
| Subtracting Mixed Numbers
[M] |
When the top fraction part is too small, break one whole into d parts. |
| Whole Number × Unit Fraction
[E] |
n copies of 1/d stack up to n/d - multiplication is repeated addition. |
| Multiplying a Fraction by a Whole Number
[M] |
n × a/b is n × a of the 1/b pieces: multiply the top, keep the bottom. |
| Tenths & Hundredths as Decimals
[E] |
Decimals are just fractions with denominators 10 and 100 in disguise. |
| Adding Tenths and Hundredths
[M] |
Trade every tenth for ten hundredths, then add same-size pieces. |
| Comparing Decimals to Hundredths
[M] |
Longer doesn't mean larger - line up the tenths place and compare. |
| Fraction Word Problems
[M] |
Pick the picture first - parts left over, laps repeated, or days combined. |
| Angles as Turns
[E] |
An angle measures how far one ray turns away from another. |
| Adding Angles
[E] |
A ray through an angle cuts it into parts that add up to the whole. |
| Finding Missing Angles
[M] |
Subtract the known parts from 90°, 180°, or 360° to find the rest. |
| Classifying Triangles
[E] |
Sort triangles by their angles or by how many sides match. |
| Classifying Quadrilaterals
[M] |
Name quadrilaterals by their parallel sides and right angles. |
| Lines of Symmetry
[E] |
A line of symmetry folds a shape exactly onto itself. |
| Perimeter Word Problems
[M] |
Fence, frame, and rope problems: work the perimeter formula backward too. |
| Area Word Problems
[M] |
Tiles, rugs, and L-shaped rooms: multiply, divide back, or split and add. |
| Kilometers, Meters & Centimeters
[E] |
Move between km, m, and cm with the anchors 1,000 and 100. |
| Kilograms & Grams
[E] |
1 kilogram is 1,000 grams - convert first, then solve the story. |
| Hours, Minutes & Seconds
[E] |
Time converts by sixties: hours to minutes to seconds. |
| Line Plots with Fractions
[M] |
Read X-mark plots in quarter units, then count, compare, and total. |
| Equivalent Fractions on a Number Line
[E] |
The same point on the line has many names - finer ticks, bigger numbers. |
| Recognizing Equivalent Fractions
[E] |
Multiply top and bottom by the same number - never add the same number. |
| Comparing with Common Denominators
[M] |
Give both fractions the same size pieces, then just count them. |
| Ordering Three Fractions
[M] |
Put them over one common denominator and the order reads straight off. |
| Adding Like-Denominator Fractions in Context
[E] |
Same-size pieces just pile up - add the numerators, keep the denominator. |
| Subtracting Like-Denominator Fractions
[E] |
Take pieces away from same-size pieces - subtract the tops, keep the bottom. |
| Mixed-Number Addition Word Problems
[M] |
Add the wholes, add the parts, then trade a full set of parts for a whole. |
| Mixed-Number Subtraction Word Problems
[M] |
When the fraction you take is too big, break one whole into d parts. |
| Fraction × Whole Number Word Problems
[M] |
n groups of a/b is n×a of the 1/b pieces - multiply the top, keep the bottom. |
| Decimal Notation for Tenths & Hundredths
[E] |
A decimal is a fraction with denominator 10 or 100, written by place. |
| Relating Fractions and Decimals
[M] |
3/10 and 0.3 are the same amount - two ways to write one number. |
| Comparing Decimals in Context
[M] |
Line up the tenths place first - more digits does not mean more value. |
| Adding Tenths and Hundredths
[M] |
Trade each tenth for ten hundredths, then add same-size pieces. |
| Length Problems: Convert, Then Combine
[M] |
Turn every length into one unit first, then add or subtract. |
| Mass Problems: Kilograms and Grams
[M] |
Convert kilograms to grams, then total, take away, or compare. |
| Liquid Volume: Liters and Milliliters
[M] |
Liquid volume converts like mass: 1 liter is 1,000 milliliters. |
| Time Problems: Hours, Minutes, Seconds
[M] |
Change to one time unit using sixties, then add or subtract. |
| Elapsed Time Across the Hour
[M] |
Total the minutes across each o'clock, then adjust for breaks. |
| Perimeter: Finding a Missing Side
[M] |
Perimeter is the total edge, so a missing side is the total minus the rest. |
| Area: Finding a Missing Length
[M] |
Area is length times width, so divide the area by a known side. |
| Area of Rectilinear Figures
[M] |
Split an L or staircase into rectangles, or subtract a cut-out corner. |
| Line Plots: Fraction Questions
[M] |
Read a fraction line plot to find spread, totals, and combined lengths. |
| Adding Angles on a Diagram
[M] |
Angle measure adds up: parts total the whole, and rays split it. |
| Classifying Angles and Triangles
[M] |
Sort angles as acute to reflex, and triangles by angles or sides. |
| Money: Change and Multi-Step Spending
[M] |
Total the cost, subtract from what is paid, then spend the change. |
| Adding Within 1,000,000
[E] |
Stack six-digit numbers by place value and carry across every column. |
| Subtracting Within 1,000,000
[E] |
Regroup across many columns to subtract six-digit numbers. |
| Estimating Sums & Differences
[E] |
Round each number first to get a quick check on a big sum or difference. |
| Two-Digit by Two-Digit Multiplication
[M] |
Multiply by the tens and the ones, then add the two partial products. |
| Four-Digit by One-Digit Multiplication
[M] |
Multiply each place of a four-digit number by the single digit, carrying up. |
| Estimating Products
[M] |
Round the factors to easy numbers to predict roughly how big a product is. |
| Dividing by a One-Digit Number
[M] |
Long-divide a three- or four-digit number that comes out even. |
| Division with Remainders
[M] |
When the divisor doesn't fit evenly, whatever is left is the remainder. |
| Estimating Quotients
[M] |
Swap the dividend for a nearby number the divisor divides evenly. |
| Understanding Remainders
[M] |
A remainder is always smaller than the divisor, and rebuilds the dividend. |
| Order of Operations
[M] |
Do multiplication and division before addition and subtraction. |
| Parentheses First
[M] |
Whatever is inside parentheses gets done before anything else. |
| Multi-Step Expressions
[M] |
Combine several operations in one expression, obeying the full order rules. |
| Adding Mixed Numbers with Regrouping
[M] |
When the fraction parts spill past one whole, carry a whole and keep the rest. |
| Subtracting Mixed Numbers with Regrouping
[M] |
When the top fraction is too small, borrow one whole and turn it into d parts. |
| Combining Mixed Numbers Toward a Goal
[M] |
Add up what is done, then subtract from the goal to see what is left. |
| Multiplying Fractions in Word Problems
[M] |
n groups of a/b is n×a of the 1/b pieces - multiply the top, keep the bottom. |
| Fractions Against the 1/2 Benchmark
[M] |
A fraction beats 1/2 exactly when its top is more than half its bottom. |
| Ordering Fractions with Common Denominators
[M] |
Rewrite them all over one common denominator, then order the numerators. |
| Ordering Decimals
[M] |
Compare place by place from the left - tenths first, then hundredths. |
| Adding Tenths and Hundredths
[M] |
Trade every tenth for ten hundredths, then add same-size pieces. |
| Money as Fractions and Decimals
[M] |
0.25 = 1/4 = a quarter - one value, three ways to name it. |
| Coins as Fractions of a Dollar
[M] |
Count the cents, then name the total as a fraction or a decimal dollar. |
| Fractions of a Length
[M] |
Split the whole length into equal parts, then take as many as the top says. |
| Fractions of Time and Capacity
[M] |
The same part-of-a-whole idea works on minutes, liters, and hours. |
| Adding Mixed-Number Measurements
[M] |
Combine measured amounts by adding wholes, adding parts, and carrying. |
| Four Operations, Bigger Numbers
[M] |
Chain add, subtract, multiply, and divide through one larger story. |
| Scale Up, Then Share Out
[M] |
Build a big total by multiplying, then divide it into equal groups. |
| Money in Several Steps
[M] |
Unit prices, totals, and change - thinking in whole cents keeps it exact. |
| Factor Pairs in Arrays
[M] |
Every equal-row arrangement of objects matches a factor pair. |
| Prime or Composite in Context
[M] |
Whether a group splits into equal teams depends on prime vs. composite. |
| Making Identical Groups
[M] |
A common factor of two amounts is a group size that divides both. |
| Later Terms of Number Patterns
[M] |
Apply the rule step by step to reach a term far down the pattern. |
| Growing Shape Patterns
[M] |
A figure pattern that grows by a fixed amount is a number pattern in disguise. |
| Features of a Pattern
[M] |
Spot the always-true property hidden in a pattern's rule. |
| Interpreting Remainders
[M] |
Round up, drop it, or report it - the story decides what a remainder means. |
| Remainders in Multi-Step Problems
[M] |
Build the total first, then divide and read the remainder the story's way. |
| Times as Many, Both Directions
[M] |
Multiply to scale up, divide to scale back, and subtract for the gap. |
| Mixing 'More Than' and 'Times as Many'
[M] |
Untangle a story that adds one comparison and multiplies another. |
| Rounding to a Given Place
[M] |
Look one place to the right, then round the target digit up or down. |
| Value of a Digit
[M] |
A digit's value is the digit times what its place is worth. |
| Expanded Form to Standard Form
[M] |
Expanded form spells out each place's value; add them for the number. |
| Reading Number Names
[M] |
Translate the words for each place group into digits. |
| Is the Estimate Reasonable?
[M] |
Round each number first, then add to judge a sensible total. |
| Rounding to Estimate a Quantity
[M] |
Real amounts are often reported to the nearest hundred or thousand. |
| Mixed Numbers to Improper Fractions
[M] |
Multiply the whole by the denominator, then add the numerator. |
| Improper Fractions to Mixed Numbers
[M] |
Divide the top by the bottom: the quotient is the whole, remainder the top. |
| Missing Part of an Equivalent Fraction
[M] |
Whatever you multiply the bottom by, multiply the top by the same. |
| Simplest Form
[M] |
Divide the top and bottom by their greatest common factor. |
| Fraction of a Set
[M] |
Split the set into equal groups, then take as many as the numerator says. |
| Least Common Multiple
[M] |
The LCM is the smallest number both counts land on when you skip-count. |
| Greatest Common Factor
[M] |
The GCF is the largest number that divides both amounts evenly. |
| Input-Output Tables
[M] |
Apply the rule's steps in order to turn an input into its output. |
| Finding the Rule of a Table
[M] |
Test a candidate rule against every row of the table. |
| Parallel and Perpendicular Lines
[M] |
Parallel lines never meet; perpendicular lines cross at a square corner. |
| Points, Lines, Rays, and Segments
[M] |
A point is a spot; lines, rays, and segments differ by their endpoints. |
| An Angle as a Fraction of a Turn
[M] |
A full turn is 360°, so a fractional turn is that fraction of 360. |
| Comparing Area and Perimeter
[M] |
Area multiplies the sides; perimeter adds all four - they can differ. |
| Decimals on a Number Line
[M] |
Splitting 0 to 1 into 10 parts marks tenths; into 100 parts, hundredths. |
| Equivalent Fractions in an Array
[H] |
One row of an array names the same amount two ways: by rows and by dots. |
| Splitting Every Piece into More Pieces
[H] |
Cutting every piece into k pieces multiplies the top and bottom by k. |
| A Chain of Equal Fractions
[H] |
In a chain of equal fractions the top and bottom grow by the same factor. |
| The Fraction That Does Not Belong
[H] |
Two fractions are equal only when one comes from the other by one factor. |
| Whole Numbers Written as Fractions
[H] |
Every whole number is a fraction: w wholes hold w times d of the d-ths. |
| Equivalent Fractions on a Ruler
[H] |
One mark on a ruler has many names, one for each size of piece. |
| Comparing Fractions with the Same Top Number
[H] |
With equal top numbers, the smaller bottom number gives the larger fraction. |
| Comparing by the Missing Piece
[H] |
A fraction just short of one whole is larger when its missing piece is smaller. |
| Comparing by Renaming Just One Fraction
[H] |
When one bottom number divides the other, rename only that fraction. |
| Between 0, One Half, and One
[H] |
Doubling the top number and comparing it with the bottom locates a fraction. |
| Who Had More? Comparing in a Story
[H] |
Comparing fractions of the same whole answers who has more in a story. |
| Comparing Fractions in a Table
[H] |
Reading a table of fractions means comparing every row, not just two. |
| Missing Addend with Like Denominators
[H] |
An unknown part of a fraction sum is found by subtracting the known part. |
| Adding Three or Four Like Fractions
[H] |
Same-size pieces add by counting pieces, however many parts there are. |
| Subtracting from One Whole
[H] |
Write one whole as d/d before taking a fraction away from it. |
| Subtracting a Fraction from a Whole Number
[H] |
Trade one whole for d/d, then subtract the fraction from those pieces. |
| Sums That Pass One Whole
[H] |
A sum of d or more d-ths is renamed as wholes plus the leftover pieces. |
| Adding When One Bottom Number Fits the Other
[H] |
Rename the larger pieces as the smaller ones, then add the top numbers. |
| Subtracting When One Bottom Number Fits the Other
[H] |
Rename first so both fractions count the same size piece, then subtract. |
| Fifths and Tenths Together
[H] |
Each fifth is two tenths, which links fifths to decimal notation. |
| Thirds and Sixths Together
[H] |
Halves and thirds both rename as sixths, so sixths add all three. |
| Mixed Numbers on a Number Line
[H] |
A point past 1 names whole steps plus the parts counted after them. |
| How Many Wholes Are Hiding?
[H] |
Dividing the top by the bottom counts the whole wholes inside a fraction. |
| Mixed Number against Improper Fraction
[H] |
Write both amounts the same way, then compare their top numbers. |
| Adding a Fraction onto a Mixed Number
[H] |
Add the fraction parts first, then carry any whole into the whole number. |
| How Much More to the Next Whole?
[H] |
The gap to the next whole is the bottom number minus the fraction's top. |
| Totaling Mixed Numbers from a Table
[H] |
Read each amount from the table, then add or subtract the mixed numbers. |
| From Repeated Addition to Multiplication
[H] |
Adding a/b n times is the same as n times a/b, so the top is multiplied. |
| How Many Copies Make One Whole?
[H] |
Counting copies of a fraction that fill a whole asks how many fit in d/d. |
| Is the Product More Than One Whole?
[H] |
Compare n times a with the bottom number to judge the product's size. |
| Equal Groups of a Fraction
[H] |
Equal groups of unit-fraction pieces total the number of pieces over d. |
| Naming the Point on a Fraction Line
[H] |
The bottom number counts the parts in one whole; the top counts the marks. |
| Jumping by Fractions on a Number Line
[H] |
Each jump of one d-th moves the point one mark along the line. |
| Decimals in Words
[H] |
The words name the last place, which fixes how many decimal places to write. |
| Tenths or Hundredths? Watch the Zero
[H] |
A zero in the tenths place makes the next digit count hundredths, not tenths. |
| Renaming Tenths as Hundredths
[H] |
One tenth is ten hundredths, so a tenths top number times ten gives hundredths. |
| Decimals Greater Than One
[H] |
The digits before the point are the wholes; the digits after are the parts. |
| Comparing a Fraction with a Decimal
[H] |
Write the fraction in hundredths, then compare it with the decimal. |
| Locating a Decimal Between Two Tenths
[H] |
Between two tenths the line is cut into hundredths, one per small step. |
| One Point, Two Names
[H] |
A point on a tenths line has one fraction name and one decimal name. |
| Decimals That Make One Whole
[H] |
Two decimals make one whole when their hundredths add to one hundred. |
| Reading Tenths from a Bar Graph
[H] |
Bars counted in tenths become decimals once the count is placed after the point. |
| How Many Full Containers?
[H] |
Counting completely filled containers keeps only the whole number, dropping the leftover. |
| How Many Containers Are Needed?
[H] |
Holding every last piece needs one extra container for the leftover part. |
| How Much Is Left Over?
[H] |
The leftover is the remainder of pieces, written over the same bottom number. |
| Enough or Not Enough?
[H] |
Deciding whether an amount suffices compares what you have with what is needed. |
| Who Used the Most? Reading a Table
[H] |
Compare every row of amounts, wholes first and then the fraction parts. |
| Counting On by a Fraction
[H] |
Counting on by a/d repeatedly adds a pieces, so the nth number is n times a over d. |
| Completing a Conversion Table
[H] |
Each row of a conversion table multiplies by the same fixed number. |
| Regrouping a Total into Mixed Units
[H] |
Divide by the conversion number: the quotient is the big units, the remainder the small ones. |
| Comparing Measurements in Different Units
[H] |
Rewrite both measurements in the same unit before deciding which is greater. |
| Ordering Three Measurements
[H] |
Convert every measurement to one unit, then order the plain numbers. |
| Inches, Feet, and Yards
[H] |
One foot is 12 inches and one yard is 3 feet, so multiply to go smaller. |
| Pounds and Ounces
[H] |
One pound is 16 ounces, so multiply pounds by 16 to get ounces. |
| Cups, Pints, Quarts, and Gallons
[H] |
Each step down the customary capacity ladder doubles, except gallon to quart. |
| Adding Mixed-Unit Measurements
[H] |
Change every measurement to the small unit, then add the totals. |
| Subtracting Mixed-Unit Measurements
[H] |
Convert both measurements to the small unit, then subtract. |
| Multiplying a Mixed-Unit Measurement
[H] |
Convert one item to the small unit, multiply, then finish the story. |
| Choosing a Sensible Unit
[H] |
Match the size of the unit to the size of the thing being measured. |
| Two-Step Conversions
[H] |
Convert one step at a time, multiplying down the ladder or dividing up it. |
| Perimeter of a Regular Polygon
[H] |
A regular polygon has equal sides, so its perimeter is the side length times the number of sides. |
| Perimeter of an L-Shaped Figure
[H] |
Add every side of a rectilinear figure; cutting a corner leaves the perimeter unchanged. |
| Missing Sides of an L-Shaped Figure
[H] |
Facing sides of an L-shape match, so a missing piece is the whole minus the known piece. |
| Same Area, Different Perimeter
[H] |
Rectangles with equal areas can have different perimeters; divide the area by one side to find the other. |
| Same Perimeter, Different Area
[H] |
Rectangles with equal perimeters can have different areas; half the perimeter is length plus width. |
| Squares: Side, Perimeter, and Area
[H] |
A square has four equal sides, so perimeter is four times a side and area is a side times itself. |
| Cost of Covering an Area
[H] |
Find the area first, then multiply by the price for each square unit. |
| Cost of Fencing a Border
[H] |
Fencing follows the perimeter, so find the distance around and multiply by the price per meter. |
| Area of a Border Path
[H] |
Subtract the inner rectangle's area from the outer rectangle's area to get the border. |
| Elapsed Time from a Clock Face
[H] |
Read the start time off the clock, then count minutes forward to the end time. |
| Finding the Start Time
[H] |
Count backwards from the end time by the length of the event. |
| Finding the End Time
[H] |
Add the length of each stage to the start time, regrouping 60 minutes into an hour. |
| Reading a Schedule
[H] |
Subtract a start time from an end time to get the length of each item on a schedule. |
| Time Spans That Cross Noon
[H] |
Count up to 12:00 noon, then add the time after noon. |
| Change with the Fewest Coins
[H] |
Find the change first, then take the largest coin that fits as many times as possible. |
| How Many Can You Buy?
[H] |
Divide the money by the price and drop the remainder, since a part of an item cannot be bought. |
| Shopping from a Price List
[H] |
Read each price from the list, multiply for repeats, add the bill, then subtract to find change. |
| Reading a Line Plot in Halves
[H] |
Each mark on a line plot stands for one measurement, so counting marks answers how many. |
| Building a Line Plot from a List
[H] |
Each measurement in a list becomes one X above its own tick on the line plot. |
| A Missing Stack on a Line Plot
[H] |
Subtract the stacks you can see from the total to find the missing stack. |
| Bar Graphs with a Scale
[H] |
When one bar unit stands for several items, multiply the bar height by that number. |
| Comparing Bars on a Graph
[H] |
Compare two bars by subtracting the shorter value from the taller one. |
| Totals from a Bar Graph
[H] |
Add every bar for the total, and subtract from a known total to find a missing bar. |
| Picture Graphs with a Key
[H] |
Multiply the number of symbols by the key value to get the real amount. |
| Comparing Rows of a Picture Graph
[H] |
Compare rows by their symbol counts, then multiply the difference by the key value. |
| Reading a Tally Chart
[H] |
Each group of tally marks crossed through stands for five, so count by fives then add the singles. |
| Two-Step Questions from a Table
[H] |
Combine two columns of a table first, then compare or total the results. |
| Estimating an Angle
[H] |
Judge an angle against the benchmarks of 90 degrees and 180 degrees. |
| Quarter Turns and Directions
[H] |
A quarter turn is 90 degrees, so each 90 degrees clockwise moves one step around the compass. |
| Angles Around a Point
[H] |
Angles that fill a complete turn around a point add to 360 degrees. |
| Angles Made by Clock Hands
[H] |
The twelve hour marks split a clock into twelve 30 degree steps. |
| Lines of Symmetry in Regular Shapes
[H] |
A regular polygon has as many lines of symmetry as it has sides. |
| Sides of a Quadrilateral from the Perimeter
[H] |
Opposite sides of a parallelogram are equal, so half the perimeter is one long side plus one short side. |
| Can These Angles Make a Triangle?
[H] |
The three angles of any triangle add to exactly 180 degrees. |
| Naming a Triangle Two Ways
[H] |
Every triangle has a name from its sides and a second name from its angles. |
| Multi-Step Measurement Problems
[H] |
Convert to one unit, work out the part that repeats, then add or subtract. |
| Leftovers: Round Up or Round Down?
[H] |
Count only complete groups when filling containers, but add one more group when nothing may be left behind. |
| Naming Places to the Millions
[H] |
Places are counted from the right: ones, tens, hundreds, thousands, and on. |
| Reading a Place-Value Chart
[H] |
A place-value chart lists one digit per place, in order from left to right. |
| Expanded Form of a Large Number
[H] |
Expanded form adds up what each digit is worth in its own place. |
| Building a Number from Clues
[H] |
Each clue fixes one digit; write the digits in place order to build the number. |
| Comparing What Two Digits Are Worth
[H] |
The same digit is worth different amounts in different places; subtract to compare. |
| Reading a Number Line of Large Numbers
[H] |
Equally spaced marks count by the same amount every jump. |
| Comparing Numbers to the Millions
[H] |
Compare place by place from the left; the first place that differs decides. |
| Rounding to Hundred Thousands and Millions
[H] |
Check the digit one place to the right, then round the target place up or down. |
| Numbers That Round to a Given Value
[H] |
Every rounded value comes from a band of numbers with a top and a bottom. |
| Rounding One Number Two Ways
[H] |
Rounding to a larger place can move a number the other direction. |
| Rounding the Numbers in a Table
[H] |
Round each value in a data table to the same place before comparing or adding. |
| Subtracting Across Zeros
[H] |
A row of zeros needs regrouping to travel several places to the left. |
| Missing Digits in a Sum
[H] |
Rebuild a hidden digit by adding one column at a time and tracking carries. |
| Missing Digits in a Difference
[H] |
Recover a hidden digit in a subtraction by checking each column, borrows included. |
| A Missing Number in a Subtraction
[H] |
Addition undoes subtraction, so it recovers a missing part and checks an answer. |
| Keeping a Running Total
[H] |
Add every amount in and subtract every amount out to track a total. |
| Comparing Two Changes
[H] |
Find each change by subtracting, then compare the changes themselves. |
| Partial Products with One Digit
[H] |
Multiply each place separately, then add the partial products. |
| Multiplying Multiples of Ten and Hundred
[H] |
Multiply the front digits, then attach every zero from both factors. |
| Finding a Missing Factor
[H] |
Divide the product by the known factor to recover the missing one. |
| The Area Model for a Two-Digit Product
[H] |
An area model splits both factors by place and multiplies every pair of parts. |
| Multiplying by a Multiple of Ten
[H] |
Multiply by the tens digit, then attach the zero that the ten carries. |
| Two-Digit Products in Stories
[H] |
Equal groups of a two-digit size multiply, and other steps follow after. |
| Comparing Two Products
[H] |
Estimate or compute each product, then compare the results. |
| Zeros Inside the Quotient
[H] |
Write a 0 in the quotient whenever the divisor does not fit into a place. |
| How Many Digits in the Quotient
[H] |
Compare the divisor with the leading digits to see where the quotient starts. |
| Naming the Quotient and the Remainder
[H] |
A full division answer names how many whole groups and how much is left. |
| How Many More Would Fill the Last Group
[H] |
The gap in the last group is the divisor minus the remainder. |
| Buying Enough Packs
[H] |
When every item must be covered, the leftover forces one more whole pack. |
| Dividing in Two Stages
[H] |
Sharing out twice divides twice; multiplying back undoes both stages. |
| Both Parts of a Division Answer
[H] |
One division answers two questions: how many full groups and how many are left. |
| Between Which Two Numbers?
[H] |
Rounding the numbers first shows which pair of landmarks the answer falls between. |
| Which Answer Is Reasonable?
[H] |
An estimate rules out answers that are ten times too big or too small. |
| Repairing an Unreasonable Answer
[H] |
Estimation flags a wrong answer; then redo the work carefully to fix it. |
| Factor or Multiple?
[H] |
The smaller number is the factor; the larger one is the multiple. |
| Counting Multiples in a Range
[H] |
Skip count through the range, or divide each end and compare the counts. |
| Divisibility Rules
[H] |
Quick digit tests tell whether 2, 3, 5 or 10 divides a number evenly. |
| Which Number Has More Factors
[H] |
List each number's factor pairs and count them before comparing. |
| Counting Primes
[H] |
Test each number for small factors; a prime has exactly two factors. |
| Patterns with a Two-Step Rule
[H] |
Apply both parts of the rule, in order, to get from one term to the next. |
| A Missing Term Inside a Pattern
[H] |
Find the rule from the terms you can see, then step into the gap. |
| Working Back to the First Term
[H] |
Undo the rule once for every step back to reach the first term. |
| How Many Steps to Reach the Goal
[H] |
Divide the distance to the goal by the step size, rounding up if any gap remains. |
| Where Do the Parentheses Go?
[H] |
Parentheses choose which operation happens first, which changes the value. |
| How Parentheses Change the Value
[H] |
The same numbers give different values depending on where parentheses sit. |
| A Missing Number in an Expression
[H] |
Undo the operations in reverse order to uncover the missing number. |
| Solving an Equation with a Letter
[H] |
A letter stands for one unknown number; undo the operations to find it. |
| Write an Equation, Then Solve
[H] |
Turn the story into an equation with a letter before doing any arithmetic. |
| Two Steps from a Price List
[H] |
Read the prices from the list, then multiply and add or divide as the story asks. |
| Two Steps from a Bar Graph
[H] |
Read the bars first, then add, subtract or compare to answer the question. |