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 Broken Calculator (Posted on 2005-01-20)
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)

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 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

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