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Smarter Ways to Subtract

When we were at school, we really only learned the one traditional way to subtract numbers. This is where you subtract from left to right. We called it carrying or borrowing, and it’s now called re-grouping. You may remember this?

Traditional Method to Subtract


Let’s say we are subtracting 156 from 360.

subtraction traditional method

 

 

 

 

 

 

We start from the right, and immediately have to borrow.

subtraction traditional method
 

 

 

 

 

 

 

Then you subtract the tens column.

subtraction traditional method
 

 

 

 

 

 

 

 

And finally, the hundreds column – the left column.

subtraction traditional method
 

 

 

 

 

 

 

 

And there’s your answer.


However, there are easier ways to help our kids learn to subtract. Here are some of those methods. We call them mental math, Singapore method and counting up.

Mental Math

In mental math you subtract from left to right. You start with the hundreds. So, 360 – 100.

subtraction mental math
 

 

 

 

 

 

 

 

 

Then the tens, so 260 – 50.

subtraction mental math
 

 

 

 

 

 

 

 

 

 

 

And finally the ones column: 210 – 6.

subtraction mental math
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Singapore Method


In the Singapore method, you don’t have to carry over the number. In our example, 6 is greater than 0. So to avoid carrying, we’ll subtract 6 from both numbers.

subtraction Singapore math
 

 

 

 

 

 

Subtract 6 from the top line:

subtraction Singapore math 

 

 

 

Subtract 6 from the bottom line:

subtraction Singapore math
 

 

 

And then subtract the sums of those numbers, which is now a straight subtraction with no carrying:

subtraction Singapore math
 

 

 

 

 

 

Counting Up


This is a good for example for when you need to give change.


In this method, you start from the lower number and count up to the top number.
So we start with $1.56 and count up to $3.60.
First, let’s add up to tens. Adding 4 to 1.56 brings it up to 1.60.

subtraction counting up
 

 

 

 

 

 

 

 

 

 

Then, add up to 100s. Adding 50 to 1.60 brings you up to 2.00.

subtraction counting up
 

 

 

 

 

 

 

 

 

 

Then, keep counting up. Adding 1 to 2, brings us up to 3.00.

subtraction counting up
 

 

 

 

 

 

 

 

 

 

 

 

 

 

And finally, let’s add the .6 to 3 to bring it to 3.60.

subtraction counting up
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

To work out the difference between 1.56 and 3.60, you now add the numbers in orange.


0.60 + 0.4 + 1 + 0.04 = 2.04


If you are looking for practice sheets for subtracting larger numbers in columns, check out our grade 4 subtraction worksheets:


Subtract 3-digit numbers   

Subtract 4-digit numbers