Question

twenty light bulbs are tested to see if they claims last long as the manufacturers claims they do. three light bulbs failed the test. two light bulbs are selected at random without replacement from this collection of bulbs find the probability that both light bulbs failed the test. round your answer to the to three decimal places

Answer 1

prob = (3/20)(2/19) = 3/190

same question as:

I have 20 marbles of which 3 are red
I choose 2 without replacement, what is the probability that they are both red