nP6 = n*(n-1)*(n-2)*(n-3)*(n-4)*(n-5) (6 factors). nP5 = n*(n-1)*(n-2)*(n-3)*(n-4) (5 factors) The condition gives you this equation n*(n-1)*(n-2)*(n-3)*(n-4)*(n-5) = 3 * n*(n-1)*(n-2)*(n-3)*(n-4). Cancel n*(n-1)*(n-2)*(n-3)*(n-4) in both sides. You will get n-5 = 3. Answer. n = 8.