# Subtracting one 3-digit or 4-digit number from another

## Home learning focus

In this lesson, you will learn how to subtract 3 and 4-digit numbers.

This lesson includes:

• one video

• two slideshows

• one activity sheet

# Learn

First, let's recap the basics of column subtraction with this video from KS2 Maths.

## Subtraction

• If numbers are too high or too difficult to subtract in your head, you can write them down in columns.
• Separate the numbers into ones, tens, hundreds and thousands.
• List the numbers in a column and always start with the ones first.

• Estimate first and check afterwards - it's a good idea to estimate a rough answer first. And always check your actual answer.

• Subtraction is the opposite to addition, so subtraction can always be checked by adding. For example you can check that 182 - 37 = 145 by doing the sum: 145 + 37 = 182

• Look out for these words in problems: take away, difference, less than, minus, decrease, fewer than, reduce. They all indicate subtraction.

## Column subtraction

Numbers can be subtracted using the column method.

## What is 548 - 125? Start from the ones column: 8 - 5 = 31 of 4 In the tens column: 40 - 20 = 20. 2 is written in tens column as this is worth 202 of 4 In the hundreds column: 500 - 100 = 400. 4 is written in the hundreds column as this is worth 4003 of 4 The finished subtraction - 4234 of 4

When subtracting two numbers in a place value column, if the second number is larger than the first it cannot be subtracted. You need to exchange a digit from a higher column.

## What is 343 - 237? Start from the ones column: 3 - 71 of 5 It is not possible to subtract 7 from 3 so exchange one ten from the tens column for ten units: 13 - 7 = 62 of 5 In the tens column, one 10 has been exchanged so 40 becomes 30: 30 – 30 = 03 of 5 In the hundreds column: 300 - 200 = 100. 1 is written in the hundreds column as this is worth 1004 of 5 The finished subtraction - 1065 of 5

Can you think how this method could be extended to subtract two 4-digit numbers from each other? Why not give it a try by choosing two random 4-digit numbers?

# Practise

## Activity 1

Now you've learnt more about subtracting numbers, have some fun with this activity from Twinkl.