Solution of Mental ability questions

Hi, this topic is for those who have doubts in any questions or in solution of the questions.  There will be many with doubts and more people who knows the solution.  People who have doubts, please post your doubts here and those who know the solution, I request them to post the same.

Here I post my first doubt.

How to solve the question, Sasi and Suni independently complete a piece of work in 8 hours and 9 hours respectively.  If they work together, how much time wil be required to complete the work?

I would be grateful if anyone please explain the step by step solution so that I can solve any such questions.


Edited by kvshivu - 02 Dec 2009 at 8:10pm

Which is the missing fraction in the following series? 2/3 4/7 ?/? 11/21 16/31

6/11

5/18

7/13

5/9

9/17

Edited by aknidhin - 22 Jan 2010 at 3:42pm

17 hours