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Coins

by fr743 » Sat Jul 16, 2011 12:44 am
Three coins are drawn at random from a pile
containing only 9 nickels and 10 dimes. If the
first two coins drawn are nickels, what is the
probability that the next coin drawn will be a
dime?

(A) 0
(B)7/17
(C)10/17
(D)10/19
(E) 1

Help me please. Explain.
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by Anurag@Gurome » Sat Jul 16, 2011 3:08 am
fr743 wrote:Three coins are drawn at random from a pile containing only 9 nickels and 10 dimes. If the first two coins drawn are nickels, what is the probability that the next coin drawn will be a dime?
After drawing two nickels, (10 + 9 - 2) = 17 coins are left.
Out of them 10 are dimes.

Hence, required probability = 10/17

The correct answer is C.
Anurag Mairal, Ph.D., MBA
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