All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Just Math
Broken Calculator (Posted on 2005-01-20) Difficulty: 3 of 5
You have a calculator whose multiplication button is broken. The only operations that work are addition (x+y), subtraction (x-y), and reciprocation (1/x).

Can you use this calculator to multiply two numbers?

See The Solution Submitted by David Shin    
Rating: 3.6250 (8 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution A slightly different methodology Comment 14 of 14 |

Any given number (n, say) can be divided by 2 in the following manner:

n/2 = 1/(1/n + 1/n)........(i)

Any given number (m, say) can be squared by way of the following
identity:

m^2 = m + 1/(1/(m-1) - 1/m) ..........(ii)

The product of two given numbers P and Q can be calculated in
the following way:

(P+Q)^2 - P^2 - Q^2 (Rule (ii))

= 2PQ

-> 2PQ/2 = PQ (Rule (i))  

*** Nice Problem

Edited on April 5, 2007, 11:34 am
  Posted by K Sengupta on 2007-04-03 05:58:55

Please log in:
Login:
Password:
Remember me:
Sign up! | Forgot password


Search:
Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (8)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:
Copyright © 2002 - 2017 by Animus Pactum Consulting. All rights reserved. Privacy Information