Posted by Pandey ji on Thursday, May 16, 2013 at 10:22pm.
Let Pn be the set of all subsets of the set [n]={1,2,…,n}. If two distinct elements of P5 are chosen at random, the expected number of elements (of [n]) that they have in common can be expressed as a/b where a and b are coprime positive integers. What is the value of a+b?

math  aaron, Friday, May 17, 2013 at 6:29am
136

math  Athul, Friday, May 17, 2013 at 8:31am
wrong
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