AAPL wrote:GMAT Prep
A magician has five animals in his magic hat: 3 doves and 2 rabbits. If he pulls two animals out of the hat at random, what is the chance that he will have a matched pair?
A. 2/5
B. 3/5
C. 1/5
D. 1/2
E. 7/5
AND means MULTIPLY.
OR means ADD.
Case 1: 2 doves
P(1st animal is a dove) = 3/5. (Of the 5 animals, 3 are doves.)
P(2nd animal is a dove) = 2/4. (Of the 4 remaining animals, 2 are doves.)
Since in Case 1 we need the 1st animal to be a dove AND the 2nd animal to be a dove, we MULTIPLY the fractions:
3/5 * 2/4 = 6/20 =
3/10
Case 2: 2 rabbits
P(1st animal is a rabbit) = 2/5. (Of the 5 animals, 2 are rabbits.)
P(2nd animal is a rabbit) = 1/4. (Of the 4 remaining animals, 1 is a rabbit.)
Since in Case 2 we need the 1st animal to be a rabbit AND the 2nd animal to be a rabbit, we MULTIPLY the fractions:
2/5 * 1/4 = 2/20 =
1/10
Since a good outcome will be yielded by Case 1 OR by Case 2, we ADD the blue fractions:
3/10 + 1/10 = 4/10 = 2/5
The correct answer is
A.
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