gmat prep

xuelb

on his drive to work, Leo listens to one of three radio stations, A , B or C. He first turns to A. If A is playing a song he likes, he listens to it; if not, he turns to B. If B is playing a song he likes, he listens to it; if not, he turns to C. If C is playing a song Leo likes, he listens to it; if not, he turn off the radio. For each station, the probability is 0.3 that at any given moment the station is playing a song Leo likes. On his drive to work, what is the probability that Leo will hear a song he likes.

0.027     0.090      0.417     0.657    0.900

the answer is D.

looking forward to an expert's explanation.

满溪

listen to A 0.3, liaten to B 0.7*0.3，listen to C 0.7*0.7*0.3, all together 0.3+0.7*0.3+0.7*0.7*0.3=0.657

xuelb

以下是引用满溪在2006-4-30 2:48:00的发言：
listen to A 0.3, liaten to B 0.7*0.3，listen to C 0.7*0.7*0.3, all together 0.3+0.7*0.3+0.7*0.7*0.3=0.657

谢谢，我脑袋进水了