The number of ways in which 10 boys can be divided into 2 groups of 5 , such that two tallest boys are in two different groups, is equal to

Step-by-step solution

Excluding the 2 tallest boys, we can divide the 8 boys into 2 groups of 4 each by 8 ! 4 ! 4 ! 2 ! ways. The tallest boys can be assigned to the groups in 2 ways. The desired number of ways are 8 ! 4 ! 4 ! 2 ! × 2 ! = 8 × 7 × 6 × 5 4 × 3 × 2 = 70