First slide

Permutations

Question

The number of ways of arranging 20 boys so that 3 particular boys are separated is

Moderate

A

9(16!)
B

15(16!)
C

15(17!)/2
D

none of these

Solution

We can arrange remaining 17 boys in 17! ways. For 3 particular boys we have 18 positions. We can arrange
3 particulars boys at these places in $^{18} P_{3}$ ways. Thus, the required number of ways
$= (17!) (^{18} P_{3}) = 17! \frac{18!}{15!}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App