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March 30, 2015

March 30, 2015

Posted by **Brandi** on Sunday, April 13, 2014 at 8:10pm.

Five cards are chosen from a deck of playing cards and put into a pile. Three of the cards are red and 2 of the cards are black. A second pile is made using 2 red cards and b black cards. One card from each pile is chosen randomly. The probability of choosing a red card from each of the piles is 6/45. How many black cards, b , are in the second pile? The answer is 7 but I don't know why that is the answer. Thanks...

- Math -
**Steve**, Sunday, April 13, 2014 at 11:49pmcall the 2 piles x and y

P(x) = 3/5

P(y) = 2/(b+2)

3/5 * 2/(b+2) = 6/45

6 / 5(b+2) = 6/45

5(b+2) = 45

b+2 = 9

b = 7

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