Brain Teasers
Brain Teasers Trivia Mentalrobics Games Community
Personal Links
Submit a Teaser
Your Favorites
Your Watchlist
Browse Teasers
All

Cryptography
Group
Language
Letter-Equations
Logic
Logic-Grid
Math
Mystery
Optical-Illusions
Other
Probability
Rebus
Riddle
Science
Series
Situation
Trick
Trivia

Random
Daily Teasers
Search Teasers

Advanced Search
Add to Google Add to del.icio.us

More ways to get Braingle...

5 * 7 = 37

Math brain teasers require computations to solve.

 

Puzzle ID:#29101
Fun:*** (2.15)
Difficulty:** (2)
Category:Math
Submitted By:DakarMorad**

 

 

 



According to basic algebra, (A + B)(A - B) is equal to A^2 - B^2 (A^2 is "A squared"). Substituting 1 for B, we get A^2 - 1^2.

A^2 - 1^2 is the same as A^2 + (-1^2). Since -1 times -1 is one, we end up with A^2 + 1.

If we substitute 6 for A, we get (6+1)(6-1) = 6^2+1, or 37. Since 6+1 is 7 and 6-1 is 5, five times seven is thirty-seven.

What's wrong with this proof?

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.

 






Back to Top
   



Users in Chat : catmandon 

Online Now: 8 users and 746 guests

Copyright © 1999-2016 | Updates | FAQ | RSS | Widgets | Links | Green | Subscribe | Contact | Privacy | Conditions | Advertise

Custom Search





Sign In A Create a free account