a.224/323 b.99/323 c.224/325 d.99/325
2006-07-20 17:49:12 · 1 answers · asked by guitarkhongday 1 in Science & Mathematics ➔ Mathematics
The answer is (b). The probability of getting a matching pair is one minus the probability of not getting a match. Here's one way to get the answer:
1. He picks a shoe at random. 2. He picks a second shoe at random. There were 19 to choose from, and 18 of the 19 were wrong. His probability of not having a match is 18/19.
3. He picks a third shoe. 16 of the 18 choices are wrong, so now his chance of not having a match is (18/19)(16/18) = 16/19.
4. He picks a fourth shoe. 14 of the 17 choices are wrong. (Notice on this last pick, there were three possible "winners" for him.) After picking four shoes, the probability of not having a match is (16/19)(14/17) = 224/323.
The probability of getting a matched pair is 1 - 224/323 = 99/323 (answer b).
2006-07-20 18:23:55 · answer #1 · answered by bpiguy 7 · 1⤊ 0⤋