stolyar
There is a group of six people; among them are Mr X and Mr Y. Three persons are chosen at random without repetitions. Find the probability of choosing:
1) Mr X, but not Mr Y.
2) Both Mr X and Mr Y.
3) Neither Mr X nor Mr Y.
4) Either Mr X or Mr Y, but not both.
5) Either Mr X or Mr Y or both.
1. C[2,4]/C[3,6] = 36/120 = 6/20 = 3/10.
2. C[1,4]/C[3,6] = 4*6*6/(6*120) = 1/5.
3. C[3,4]/C[3,6] = 1/5.
4. 2*P(X, but not Y) = 6/10 = 3/5.
5. P(X or Y, but not both) + P(both) = 3/5 + 1/5 = 4/5.