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Look at this number square, which shows all the bonds you should know by heart up to 20.
You can use this table to work out additions and subtractions right up to 100.
Example 1
Add 76 + 9
Answer
We split 76 into 70 and 6.
We now need to work out
70 + 6 + 9
You should know this by heart, but the number square shows that
6 + 9 = 15
So
76 + 9 = 70 + 6 + 9
= 70 + 15 = 85
Example 2
Subtract 85 - 9
Answer
We split 85 into 70 and 15.
We now need to work out
70 + 15 - 9
You should know this by heart, but the number square shows that
15 - 9 = 6
When you subtract, the starting number is inside the square.
So
85 - 9 = 70 + 15 - 9
= 70 + 6 = 76
