Permutations — MATHS STD 11 Science — Question

First person can be seated in a row in 6 ways. Second person can be seated in a row in 5 ways. Third person can be seated in a row in 4 ways. Fourth person can be seated in a row in 3 ways. Fifth person can be seated in a row in 2 ways. And, sixth person can be seated in a row in 1 ways. Hence, total number of ways in which six persons can be seated in a row = 6 × 5 × 4 × 3 × 2 × 1 = 720.