Between 10 A.M. and 11 A.M., 48 people came into Brad's store. 40 of them * made a purchase. What is the total number of trials?

Answer: 

IB Math HL, probability question (see screenshot) THANKS!

3. Chris knows that his chance to catch an elevator without having to wait for it on a Monday is 1, while on a Tuesday or a Wednesday, he is twice as likely to wait as he is not to wait. He will choose one of these days: Monday with probability 0.4, Tuesday with probability 0.3, and Wednesday with probability 0.3 for his elevator ride. What is the probability that he has to wait for the elevator? (A) 0.8 (B) # (C (D) E) 0.6

Suppose a weather forecast reports that the probability of snow this week is 0.18. The forecast states that if it snows this week, the probability that it snows next week is 029. If it does not snow this week, the probability that it snows next week is 0.12. The tree diagram depicts the possible weather event outcomes with the asociated probabilities. What is the probability that it will snow next week? Provide your answer with precision to two decimal places.