A={1,2,3,...........50}


i want to find out the total possible power sets

some body tell me the total sets which are possible
i find that the quantity by this formula 2(n*n)
2(50*50)
2*2500
50,000
possible sets are 50,000
but i need only those pairs which containes only five elements

The total number of sets in the power set of a set with n elements is 2n. Or in your case 250 or 1,125,899,906,842,624. The total number of subsets of a set with n elements with a given size r is (nCr) or n!/((n-r)!*r!) - in your case 2,118,760.