When can I use this method?
For multiplying numbers near 10. The numbers can be either more than 10 or less than 10 or a combination of the two.
You may also use this method to multiply numbers a little farther away from 10 as long as their differences from 10 are easy to multiply.
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- This method uses the concept (10 + a) (10 + b) = [(10 + a) + b] + ab or [(10 + b) + a] + ab, where ‘(10 + a)’ and ‘(10 + b)’ are numbers near 10 and ‘a’ and ‘b’ are the respective differences.
- Whenever the number is more than 10, the difference is written as positive (+ve).
- Whenever the number is less than 10, the difference is written as negative (-ve).
- When both numbers are either less or more than 10, you add the product of differences.
- When one number is more than 10 and another less than 10, you subtract the product of differences.
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