Question

help: A box contains 29 widgets, 4 of which are defective. If 4 are sold at random, find the probability that (a) all are defective (b) none are defective

Answer 1

(4/24)*(3/23)*(2/22)*(1/21)
~.00009
~.009%
(b)
(20/24)*(19/23)*(18/22)*(17/21)
.45
45%

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Answer 2

Or I could say it more detailed

(a) If 4 are sold, probability that all the 4 are defective = (1/6)(1/6)(1/6)(1/6) = 1/(6^4)
= 1/1296
= 0.00077


(b) If 4 are sold, probability that none of the 4 are defective = (5/6)(5/6)(5/6)(5/6)
= (5/6)^4
= 0.48225

Now you have answer and understand?