Maths Teacher
Wednesday 5 June 2013
Easy multiplication by 9
To multiply a number by 9, multiply it by 10 and then subtract the original number.
Example: To multiply 139 by 9, first multiply 139 by 10.
139 x 10 = 1390
Next subtract 139 from 1390.
1390 – 139 = 1251
Thus 139 x 9 = 1251
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