A certain number N divided by one more than itself yields one fifth.

Another number M divided by one more than itself yields one fifth of itself.

It is quite easy to find the product M*N.

**Try to do it " by heart" i.e. no calc, no pen, no paper.**

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(In reply to

Without solving for M and N by K Sengupta)

I have found a shorter solution compared to my previous post and, this is as follows:

We have, N/(N+1) = 1/5 ..... (i)

M/(M+1) = M/5 .....(ii)

Dividing (ii) by (i), we have:

M(N+1)/N(M+1) = M

-> (N+1)/N(M+1) = 1

-> N+1 = N(M+1)

-> N+1 = M*N + N

-> M*N = 1 QED

*Edited on ***January 11, 2012, 1:29 am**