statistics

Question

A box of 11 parts contains 55 that are defective. A worker picks parts one at a time and attempts to install them. Find the probability of each outcome in? (a) through? (d).
?(a) The first two chosen are both good.

b) At least one of the first three is good.

C) The first four picked are all good.

D) The worker has to pick five parts to find one that is good.

Answer 1

did you mean a box of 11 has 5 that are defective?

most parts that can be defective are 11, 55 is impossible.

if 5 defectives, then:

a) first 2 chosen are good. 1st chosen is good has probability 6/11, 2nd then has probability 5/10=1/2

6/11 x 1/2 = 3/11 odds

b) at least 1 of 1st 3 are good = 1 minus odds all 3 are defective = 1- (5/11)(4/10)(3/9) = 1- 2/33= 31/33

c) first 3 chosen are good multiply a) by 4/9 to get 3/11 x 4/9 = 4/33 odds