A bag contains 10 marbles: 3 are green, 5 are red, and 2 are blue. Josh chooses a marble at random, and without putting it back, chooses another one at random. What is the probability that the first marble is red and the second is blue? Write your answer as a fraction in simplest form.
Answer (2)
10 5 ⋅ 9 2 = 9 1 10 a ll 5 re d ⋅ 9 a ll 2 b l u e
The probability that the first marble drawn is red and the second marble drawn is blue is 9 1 . This is calculated by multiplying the probabilities of drawing a red marble first and then a blue marble second. Thus, P ( R e d ) = 2 1 and P ( Bl u e ∣ R e d ) = 9 2 .
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