Simple Multiplication


by Henry E. Dudeney

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The number 142,857 shown in the diagram can be multiplied by 3 in an unusual but yet simple way. All that is necessary is to move the 1 to the other end of the row, and the thing is done. The answer is 428,571.

It is known there is a number that, when multiplied by 3 and divided by 2, the answer will be the same as if we moved the first digit (which in this case is to be a 3) from the beginning of the row to the end. Can you guess how many digits this number consists of? Don't be surprised by looking at the solution!

Posted: February 28, 2009
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