The first time the band leader selects one member, the probability that either you or your brother gets selected would be 2 out of 80 or in fraction 2/80. Now, once one of you gets chosen, for the next selection, there are only 79 members left and the probability that the remaining one (between you and your brother) gets selected after is 1/79. So, if you are both to be selected, the combined probability for that to happen will be (2/80)(1/79) = 1/3160. Therefore, the answer is 1/3160.
A band leader randomly selects 2 students out of 80 band members. If you and your brother are both band members, what is the probability that you are both selected?