perplexus.info :: Numbers : Duplicate Digit Determination

Duplicate Digit Determination (Posted on 2006-12-03)

If 2^P and 5^P start with the same (non-zero) digit for positive integer P, what is that digit? Can you prove it must be so?

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An easy way out

| Comment 4 of 6 |

Given that 2^5=32 and 5^5=3125 both start with 3, if there is a single answer to this problem, it must be "3".

Posted by Federico Kereki on 2006-12-03 17:51:41

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