Brain Teasers Optical Illusions Puzzle Hunts Codes & Ciphers Mechanical Puzzles
Personal Links
Browse Teasers
Search Teasers

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?

Open Calculator



What Next?

  
  

See another brain teaser just like this one...

Or, just get a random brain teaser

If you become a registered user you can vote on this brain teaser, keep track of
which ones you have seen, and even make your own.

 



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

xdbtcpAus**
Dec 15, 2014

5^2+5^1+5^0


Back to Top
   


Online Now
3 users and 566 guests

Users In Chat
autumn
Follow Braingle!
Fold 'N Fly Paper Airplanes
Easy to follow folding instructions and videos.
Copyright © 1999-2017 | FAQ | Widgets | Links | Green | Subscribe | Contact | Privacy | Conditions | Advertise | Braingle Time: 7:24 am
Sign In Create a free account