j_shreyans wrote:From a bag containing 12 identical blue balls, y identical yellow balls, and no other balls, one ball will be removed at random. If the probability is less than 2/5 that the removed ball will be blue, what is the leat no. of yellow balls that must be in a bag?
A)17
B)18
C)19
D)20
E)21
Let T = the total number of marbles.
Since the probability of selecting a blue marble is less than 2/5, the 12 blue marbles in the bag must constitute less than 2/5 of the total:
12 < (2/5)T
30 < T.
Since the total number of marbles must be at least 31, the least number of yellow marbles that must be added to the 12 blue marbles is 19.
The correct answer is
C.
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