Method I - Nines Complement Method
CPD: A Compendium of Mathematical Methods (By Jo Morgan), topic 2.1.9
Nines Complement Method: 753 − 491
Step 1
- Instead of subtracting from 753, we start by subtracting 491 from 999. It is easy to subtract any number from 999.
Step 2
- 508 is the ‘9s complement’ of 491.
- Now add 508 to 753.
Step 3
- Subtract 1000 from the total, then add 1.
- This is equivalent to subtracting 999.
Test yourself on Method I - Nines Complement Method
Which student has done the first step of the calculation 792,836 − 284,756 correctly?
Which student has done the final step of the calculation 792,836 − 284,756 correctly?