1. The problem statement, all variables and given/known data A and B decide to meet between 1pm and 2pm on a given day. Whoever arrives first will not wait for the other for more than 15 minutes. What's the probability that they will meet that day? 2. Relevant equations Probability of event occurring = (number of favorable chances)/(total number of possible chances) 3. The attempt at a solution Honestly I didn't know how to do it. The book has something like this: Let's take A arrives before B. The probability that A arrives during the first 3/4 hour is 3/4. He'll then wait 1/4 hour. The probability that A arrives during the last 1/4 hour is 1/4, and then (on average he'll wait) 1/8 hour.(This i understood. Like if A arrives at 1:45, he'll wait for maximum 15 minutes, but if A comes at 2:00, he won't wait, so average wait time is extremes/2 is (15+0)/2 is 7.5 minutes is 1/8 hours) So altogether A will wait (3/4)*(1/4 ) + (1/4)(1/8) = 7/32(i guess this is minutes. Like time for which A waits). So the probability that B arrives while A is waiting is 7/32. I didn't understand this. What is this probability? This is A waiting time. B can come anytime between 1 and 2. Similarly if B arrives before A we have P(A and B) meet is 7/32. So altogether, the probability of them meeting is 7/32 + 7/32 = 7/16.