Consider the set of five numbers 1,2,4,5,7,Two numbers are chosen from the set at radom.if the same number can be chosen more than once,find the probability that the sum of numbers chosen is even.
2.
Fred and Gary are roomates.the probabilities that Fred and Gary will clean their room this Saturday are 0.9 and 0.8 repectively.Find the probabilities that both of them clean the room,none of them clean the room,the room is cleaned this Saturday.
更新1:
In a family gathering,5 men and 3 women sit around one table.4 men and 2 women sit around another table.If one person is chosen at random from each of the tables,find the probabilities that they are of the same sex.
更新2:
補充X不用理