The Professor's Response

I am also having trouble solving this problem: A batch consists of 12 defective coils and 88 good ones. Find the probability of getting two defective coils when two coils are randomly selected if the first selection is replaced before the second is made.

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Professor McGukian

Hi Gail,
Here is how to solve this one:
P(2 defects) = P(1st is defective) * P(2nd is defective) = # of defective coils/total * # of defective coils /total = 12/100 * 12/100 = 144/10,000 = 0.01444

Hope that helps!

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