Respuesta :
There are 3! = 6 ways he can pick the 3 oldest people
Total number of permutations of any 3 from 9 = 9P3 = 9*8*7 = 504
so required probability = 6 / 504 = 1/84
Total number of permutations of any 3 from 9 = 9P3 = 9*8*7 = 504
so required probability = 6 / 504 = 1/84