Subtraction 123
Subtract 7 from 5. You can’t, so you borrow 1 from the tens column.
Put a 1 in front of the 5 to make 15 and write a small 1 alongside
the 9 in the tens column. Using our easy method, you don’t say 7
from 15, but 7 from 10 is 3, plus 5 on top gives 8, the fi rst digit of
the answer.
Ten (9 plus 1 carried) from 6 won’t go, so we have to borrow; 10
from 10 is 0, plus 6 is 6.
Nine from 2 won’t go, so we borrow again. Nine from 10 is 1, plus
2 is 3.
Four from 8 is 4. We have our answer.
You don’t have to learn or know the combinations of single-digit
numbers that add to more than 10. You never subtract from any
number higher than 10. Most of the calculation is addition. Th is
makes the calculations easier and reduces mistakes.
Test you rself
Try these for yourself:
a) 7,325 b) 5,417
- 4,568 – 3,179
The answers are:
a) 2,757 b) 2,238
Note to parents and teachers
This strategy is very important. If a student has mastered
multiplication using the simple formula in this book, he or
she has mastered the combinations of numbers that add
to 10. There are only fi ve such combinations.