How_To_Be_Good_At_Math

88 CALCULATING •^ SUBTRACTION

Subtraction

Subtraction is the opposite, or the inverse, of addition.

There are two main ways we can think about subtraction

• as taking away from a number (also called counting
  back) or as finding the difference between two numbers.

What is subtraction?

Sometimes we reduce a

number by another number.

This is called subtraction as

taking away. Look at these

oranges. When we subtract

2 oranges from 6 oranges,

there are 4 oranges left.

6

− =

− 2 =

This symbol

means subtract

or minus

This symbol

means equals

When we subtract

2 oranges from 6 oranges

we are left with 4 oranges

4

Subtracting is the opposite of adding

It’s easy to remember how to subtract, because it’s just

the opposite to addition. With addition, we add numbers

on, and with subtraction we take numbers away.

Addition

Here, the 4 has been added to 5, and

the answer is 9. We have moved the

same distance from 5 as we did when

subtracting, just in the other direction.

Subtraction facts

Let’s use this number line to subtract

4 from 5. This takes us 4 steps back

along the number line to the number 1.

0 321 4 5 6 7 8 9 10

To add, we move

from left to right

5 − 4 = 1 5 + 4 = 9

To subtract we move

from right to left

We can use a number

line for subtraction by

counting either forward

or back along the line.

−4 +4

088_089_Subtraction.indd 88 29/02/2016 18:02