Year 4 · Column Addition and Subtraction · Summary

Year 4 Column Addition and Subtraction: summary and key words

Part of the Year 4 column addition and subtraction chapter. Chapter overview · whole chapter on one page

Chapter summary

Skill	Method
Column addition	Line up ones under ones. Add from the right. If a column makes 10 or more, write the ones digit and carry the tens.
Column subtraction	Bigger number on top. Subtract from the right. If the top digit is smaller, exchange 1 from the next column (10 more in this column).
Zeros in the top number	You cannot exchange from a 0. Go left to the first column that is not 0. Each 0 you pass becomes 9.
Mental strategies	Partition; bridge through 10, 100 or 1000; compensate (add 99 = add 100, take away 1); near doubles; count up to find a difference.
Estimating	Round each number to the nearest 10, 100 or 1000, then do the easy calculation. Use ≈.
Checking	Use the inverse: check an addition by subtracting and a subtraction by adding. Compare the answer with your estimate.
Part-whole bar models	Parts added together make the whole. Whole − one part = the other part.
Comparison bar models	The gap between the bars is the difference. Bigger − smaller = difference.
Two-step problems	Read, draw a bar model, plan two steps, calculate, check. Use the same units all the way through.

I can add numbers with up to 4 digits using the column method, with carrying.
I can subtract numbers with up to 4 digits using the column method, with exchanging.
I can subtract when there are zeros in the top number, like 5,003 − 1,847.
I can add and subtract in my head by partitioning, bridging, compensating, using near doubles and counting up.
I can estimate an answer by rounding.
I can check an answer with the inverse operation.
I can use part-whole and comparison bar models.
I can solve two-step problems with money and measures and choose the right operations.

Column method: A written way to add or subtract. Numbers go one under the other with the same place values lined up.
Carry: When a column adds to 10 or more, you write the ones digit and move the tens to the next column.
Exchange: In subtraction, swapping 1 of the next column for 10 of this column (for example 1 ten for 10 ones). Also called borrowing.
Sum / total: The answer to an addition.
Difference: How far apart two numbers are. It is the answer to a subtraction.
Inverse: The opposite operation. Addition and subtraction undo each other.
Estimate: A close answer found by rounding the numbers first.
Partition: To split a number into parts, such as 346 = 300 + 40 + 6.
Bridging: Jumping to the next round number (10, 100 or 1000) and then doing the rest.
Compensate: To use an easier number and then fix the answer, such as adding 100 and taking away 1 to add 99.
Double: A number added to itself.
Bar model: A drawing of bars that shows the numbers in a problem. Part-whole models show parts and a whole. Comparison models show two amounts side by side.
Change: The money you get back when you pay more than the cost.
Two-step problem: A problem that needs two calculations to solve.