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Five 5`s

Math brain teasers require computations to solve.

 Puzzle ID: #506 Fun: (2.41) Difficulty: (1.62) Category: Math Submitted By: Squidgy

How can five 5`s equal 31?

5x5+5+5/5 (or five times five plus five plus five-fifths)=31
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 (user deleted) Nov 21, 2001 Or use base 8 base 10 5+5+5+5+5 = 25 base 8 5+5+5+5+5 = 31 thebuddhawithin Jul 04, 2004 How does base 8 work? canu Jul 14, 2004 In base 8, each place to the left is worth 8 times more than the one to its right (in the usual notation it's 10 instead of . ----- So, in base eight, the only digits are 0 1 2 3 4 5 6 7. Eight is written 10. 30 is three times eight, i.e. twenty-four. 31 is twenty-five. 100 is eight times eight, i.e. sixty-four. Subtox Mar 18, 2007 I got 31 by placing a decimal point in front of two of the fives, but I'm pretty sure that wasn't allowed... 5 X 5 + 5 + .5 + .5 = 31 Oh well, it was fun anyway. mosca Jun 26, 2007 Subtox, that was a good alternate solution! (Old math teacher!) javaguru Jan 28, 2009 I got the expected solution, but I always like to get one extra: (5! + 5 + 5) / 5 + 5 = 31 xdbtcp Dec 15, 2014 5^2+5^1+5^0