A box has 4 black, 5 red and 6 white pens, total 15. A pen is drawn, its colour noted, and it is REPLACED. Then a second pen is drawn. What is the probability that both pens are red?

Question

Accepted Answer

1/9. With replacement, draws are independent. P(red) = 5/15 = 1/3 each. P(both red) = 1/3 × 1/3 = 1/9.

A box has 4 black, 5 red and 6 white pens, total 15. A pen is drawn, its colour noted, and it is REPLACED. Then a second pen is drawn. What is the probability that both pens are red?

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