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When we are asked to subtract numbers such as 125 - 25, we can sometimes work out the answer in our heads.
However, when we are given questions with bigger numbers, we might need to use a written method.
In this activity, we'll look at the columnar method to subtract numbers.
Let's have a look at how we can use the method to subtract:
546 - 430
First, we write the numbers in columns under the correct unit ( H = Hundreds, T = tens, O = ones ).
H T O
5 4 6
4 3 0
We are going to subtract, so we must put a subtract symbol (-) to show that.
Starting at the right-hand column (ones), we subtract the bottom number from the top and write the answers underneath.
H T O
5 4 6
4 3 0
1 1 6
546 - 430 = 116
Here's another example:
H T O
7 6 9
5 3 4
2 3 5
769 - 534 = 235
We must remember to put each digit in the correct column or the answer will be wrong.
Things get a little trickier when the bottom number is bigger than the top! We then need to exchange (sometimes known as 'borrowing'). We'll look at this in another activity.
Now, why don't you have a go at answering some questions using this method?
