Braingle: 'Five 5`s' Brain Teaser

Five 5`s

Math brain teasers require computations to solve.

Puzzle ID:	#506
Fun:	(2.42)
Difficulty:	(1.64)
Category:	Math
Submitted By:	Squidgy

How can five 5`s equal 31?

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Comments

(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