Question

A committee of 8 people is to be chosen from 7 men and 5 women. What is the number of committee if a) the committee contains at least 3 men and at least 3 women, b) the oldest man or the oldest woman, but not both, must be included in the committee?

Answer 1

Answer:196 possible committees

Explanation:

Part (a): Three cases:

Case 1: 3 men and 5 women: (7 C 3) * (5 C 5) = 35 * 1 = 35; or

Case 2: 4 men and 4 women: (7 C 4) * (5 C 4) = 35 * 5 = 175; or

Case 3: 5 men and 3 women: (7 C 5) * (5 C 3) = 21 * 10 = 210

35 + 175 + 210 = 420 possible committees

Part (b): Six cases:

Cases 1–3: Oldest man included (but not oldest woman):

Case 1: 3 men and 5 women: Not possible**; therefore, 0; or

Case 2: 4 men and 4 women: 1 * (6 C 3) * (4 C 4) = 20 * 1 = 20; or

Case 3: 5 men and 3 women: 1 * (6 C 4) * (4 C 3) = 15 * 4 = 60; or

Cases 4–6: Oldest woman included (but not oldest man):

Case 4: 3 men and 5 women: (6 C 3) * (5 C 5) = 20 * 1 = 20; or

Case 5: 4 men and 4 women: (6 C 4) * 1 * (4 C 3) = 15 * 4 = 60; or

Case 6: 5 men and 3 women: (6 C 5) * 1 * (4 C 2) = 6 * 6 = 36

0 + 20 + 60 + 20 + 60 + 36 = 196 possible committees