Question

1. what is the probability that five guests of a twenty-floor hotel all stay on different floors (no pair of them are on the same floor) if,

a. Any guests can stay on any floor?

b. Two smokers of the group must stay in four smoking floors and the rest must stay in sixteen non-smoking floors.

2. Two dice ( one black and one white) are rolled simultaneously five times. What is the probability that number on the black dice be larger than on the white dice more than twice?

3. Suppose X and Y are two real numbers picked randomly and independently between 0 and 1. find [ XY greater than equal to 0.25 ].

Answer 1