BTGmoderatorLU wrote:From a group of 7 men and 6 women, five persons are to be selected to form a committee so that at least 3 men are there on the committee. In how many ways can it be done?
A) 564
B) 645
C) 735
D) 756
E) 566
The OA is D.
I'm confused with this PS question. Experts, any suggestion about how can I solve it? Thanks in advance.
We are given a group of 7 men and 6 women and need to determine the number of ways a committee of 5 can be formed with at least 3 men on the committee.
Thus, we have 3 scenarios in which at least 3 men can be selected for the 5-person committee: 3 men and 2 women OR 4 men and 1 woman OR 5 men. Let's calculate the number of ways to select the committee for each scenario.
Scenario 1: 3 men and 2 women
Number of ways to select 3 men: 7C3 = (7 x 6 x 5)/3! = (7 x 6 x 5)/(3 x 2 x 1) = 35
Number of ways to select 2 women: 6C2 = (6 x 5)/2! = (6 x 5)/(2 x 1) = 15
Thus, the number of ways to select 3 men and 2 women is 35 x 15 = 525.
Scenario 2: 4 men and 1 woman
Number of ways to select 4 men: 7C4 = (7 x 6 x 5 x 4)/4! = (7 x 6 x 5 x 4)/(4 x 3 x 2 x 1) = 35
Number of ways to select 1 woman: 6C1 = 6
Thus, the number of ways to select 4 men and 1 woman is 35 x 6 = 210.
Scenario 3: 5 men
Number of ways to select 5 men: 7C5 = (7 x 6 x 5 x 4 x 3)/5! = (7 x 6 x 5 x 4 x 3)/(5 x 4 x 3 x 2 x 1) = 42/2 = 21
Thus, the number of ways to select a 5-person committee with at least 3 men is:
525 + 210 + 21 = 756
Answer: D
