Question

what is the permutation of 7 and 2?

Answer 1

7!=7×6×5×4×3×2×1

2!=2×1

Answer 2

It is just very 2 simple thing. The P(n, r) , by definition is the notation which stands for permutations (arrangements) of r objects taken out of n objects. It can easily be shown that P(n, r) = n! /(n - r)! where n! = 1.2.3.4. …. (n -2)(n -1)n . Accordingly P(7, 4 ) = 7!/(7- 4)! = 7!/3! =840 .