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More ways to get Braingle...

Five 5`s

Math brain teasers require computations to solve.

 

Puzzle ID:#506
Fun:*** (2.42)
Difficulty:** (1.63)
Category:Math
Submitted By:Squidgy***

 

 

 



How can five 5`s equal 31?

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Answer

5x5+5+5/5 (or five times five plus five plus five-fifths)=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.
SubtoxAus*
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*us*
Jun 26, 2007

Subtox, that was a good alternate solution!
(Old math teacher!)
javaguru*us*
Jan 28, 2009

I got the expected solution, but I always like to get one extra:

(5! + 5 + 5) / 5 + 5 = 31




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