Use a calculator.
Or better yet -- remember that the digits of the product or 9 times any number will always add up to 9.
18, 27, 36, 45, 54, 63, 72, 81, 90
Another way is to multiply 9 * 10 = 90 and subtract 9 from 90.
If you forget the product of 9 and 9, what can you do to figure it out?
3 answers
pillow
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