Re: Sample Questions of ISI ME I (Mathematics) 2010 Discussion

Posted by Verma on Apr 13, 2013; 6:40pm
URL: http://discussion-forum.276.s1.nabble.com/Sample-Questions-of-ISI-ME-I-Mathematics-2010-Discussion-tp4850019p7580066.html

Thanks for solving it.
 but i have a doubt !
 When we fix 3 at the fourth place such that the arrangement is  _ _ _ 3 _ _ _,
then for the first place we will have 4 choices i.e. 1,2,4,5
for the next place we will have 3 choices left,
and consequently 2 choices for the third place.

Moving to the right of 3, we will have 3 choices i.e 6,7 and 4 or 5(depending on which number was put before 3) for the fifth place,
2 choices for the sixth place and the last one will have 1 choice.

So wont it be 4*3*2*3*2, which makes the sum 240?
However the answer given by sir is however 168 contrary to both our answers!!