If there are 62 onto mapping from a set X containing n elements to the set Y={−1,1}, then n is equal to

Let X=x1,x2,…,xnEach xi can have two images viz – 1  and 1. Thus, there are 2n mappings from X to Y. But there are exactly two map ping which are not onto. These are when all the elements are mapped to – 1 or when all the elements are mapped to 1. ∴there are 2n−2 onto mapping from X to Y Set     2n−2=62=⇒2n=64=26⇒    n=6