Kickstart 2026 with CAclubindia Pro. Get 10% OFF. Subscribe Now! Use Code: HNY10

Permutation problem

CPT 1948 views 4 replies

Guest

Q1The number of ways in which 7boys sit in a round table so that two particular boys may sit together is

A]240

B]200

C]120

D]none of these

Q2 The number of arrangement of 10 different thing taken 4 at atime in which one particular thing always occur

Explain abovetwo through giving their solution.

Replies (4)

Ankit Hinduja

Student

1227 Points Joined June 2011

1. See the formula to find no. Of persons to be seated on round table is (n-1)!. Here , any two persons should always sit together , so consider these two as one object , so we are left with 7-1 = 6 objects. Now according to formula we have (6-1)! = 120.

Ankit Hinduja

Student

1227 Points Joined June 2011

2. The formula to find out no. Of permutations /arrangements when any one object is always included is (n-1)P(r-1).. Here n=10 , r=4.. So we have 9P3=9!/(9-3)!=504