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ilyas.h
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Shortly after being put into service, some buses manufactured by a certain company have developed cracks on the underside of the main frame. Suppose a particular city has 25 of these buses, and cracks have actually appeared in 8 of them.
(i) How many ways are there to select a sample of 5 buses from the 25 for a thorough inspection?
(ii) How many of these samples of 5 buses contain exactly 4 with visible cracks?
(iii) If a sample of 5 buses is chosen at random, what is the probability that exactly 4 of the 5 will have visible cracks (to 3 dp)?
(iv) If buses are selected as in part (iii), what is the probability that at least 4 of those selected will have visible cracks (to 3 dp)?answers:
(i) 25 buses, 5 choices so: 25C5 = 53130
(ii) 5 buses, 8 broken so: (8C4)(17C1) = 1190
(iii) 53130/1190
(iv)
at least 4, so:
{(8C4)(17C1) + (8C5)(17C0)} / 25C5can you check my answers? thanks.
(i) How many ways are there to select a sample of 5 buses from the 25 for a thorough inspection?
(ii) How many of these samples of 5 buses contain exactly 4 with visible cracks?
(iii) If a sample of 5 buses is chosen at random, what is the probability that exactly 4 of the 5 will have visible cracks (to 3 dp)?
(iv) If buses are selected as in part (iii), what is the probability that at least 4 of those selected will have visible cracks (to 3 dp)?answers:
(i) 25 buses, 5 choices so: 25C5 = 53130
(ii) 5 buses, 8 broken so: (8C4)(17C1) = 1190
(iii) 53130/1190
(iv)
at least 4, so:
{(8C4)(17C1) + (8C5)(17C0)} / 25C5can you check my answers? thanks.