Homework Help: Math Finite

Posted by Amy on Thursday, December 9, 2010 at 12:31am.

A box contains 15 pens of which 4 are defective. A random sample of 3 pens is taken without replacement and without regard to order. What is the probability of selecting at least one defective pen?

Math Finite - PsyDAG, Friday, December 10, 2010 at 1:57am
What you want in the probability of selecting 1, 2 or 3 defective pens.

P of 3 = 4/15 * 3/14 * 2/13

P of 2 = 4/15 * 3/14 * 11/13

P of 1 = 4/15 * 11/14 * 10/13

The answer is the sum of those three products.

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