How_To_Be_Good_At_Math

90 CALCULATING •^ SUBTRACTION FACTS

Subtraction facts

There are some simple facts that you can learn for

subtraction to make tricky calculations much easier.

When you’ve learned them, you’ll be able to apply

them to other calculations.

Compare this

fact with the

last one

This is similar

to the first fact

• they are part
  of the same
  family of facts

These facts

are the inverses

of the doubles

we looked at

on page 82

Here's another set of subtraction facts.

This time, the second number in each

calculation is half of the first number.

These are the subtraction facts for 10. As the

number we subtract gets larger, the difference

between the two numbers gets smaller.

TRY IT OUT

Using subtraction facts

Can you use the subtraction facts

above to work out the answers to

these calculations?

Answers on page 319

10 − 10 = 0

These subtraction

facts are the opposite, or

inverse, of the addition

facts we looked at on

page 82.

10 − 0 = 10

10 − 1 = 9

10 − 2 = 8

10 − 3 = 7

10 − 4 = 6

10 − 5 = 5

10 − 6 = 4

10 − 7 = 3

10 − 8 = 2

10 − 9 = 1

2 − 1 = 1

4 − 2 = 2

6 − 3 = 3

8 − 4 = 4

10 − 5 = 5

12 − 6 = 6

14 − 7 = 7

16 − 8 = 8

18 − 9 = 9

20 − 10 = 10

1000 − 200 =?

120 − 60 =?

140 − 70 =?

100 − 30 =?

0.1 − 0.08 =?

0.4 − 0.2 =?

090_091_Subtraction_facts_Partitioning_for_subtraction.indd 90 29/02/2016 18:56