A girl has exactly 6 quarters, 7 dimes, and 10 nickels in her pocket. If she withdraws a number of these coins at random, how many coins would she have to withdraw to ensure that she has at least a 50 percent chance of withdrawing at least one quarter?	Pick:  A) 1  B) 2  C) 3  D) 4  E) 5
When the probability of NOT drawing a quarter is 50% or less, then the probability of drawing a quarter is at least 50%.   P(not drawing a quarter with 2 coins) = 17/23 * 16/22 = 136/253 &gt; 50%   P(not drawing a quarter with 3 coins) = 136/253 * 15/21 = 680/1771 &lt; 50%   The answer is 3.
<result>C</result>
A girl has exactly 6 quarters, 7 dimes, and 10 nickels in her pocket. If she withdraws a number of these coins at random, how many coins would she have to withdraw to ensure that she has at least a 50 percent chance of withdrawing at least one quarter?