Latest Gmate Aptitude Question SOLUTION: A shopkeeper has 13 washing machines out of which 5 are defective. A customer buys 3 washing machine. What is the probability that exactly one machine is defective? (a) 1/20 (b) 1

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(#M40164894) GMATE Category question Keep an EYE

A shopkeeper has 13 washing machines out of which 5 are defective. A customer buys 3 washing machine. What is the probability that exactly one machine is defective?
(a) 1/20 (b) 1/5 (c) 70/143 (d) 35/143

Asked In Gmate taasha (7 years ago)

Unsolved Read Solution (4)

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Boinibal Sreelatha  (7 years ago)

5 are defective and (13-5) are not defective so out of 3 machines 1 from defective and 2 from not defective.
(5C1x8C2)/13C3 = 70/143

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Divya Batra  (7 years ago)

answer is (c) 70/143
explanation:-
total=13
defective=5
not defective=8
so, he bought 3 machines, out of which 1 must be defective and 2 be non-defective.
so, he must bought 2 from 8(non-defective machines) and 1 from 5(defective machines).
so, answer is:-
(8 C 2 * 5 C 1) / 13 C 3 =70/143 is the answer.

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Divya Batra  (7 years ago)

sorry, answer is (d)35/143
it was my calculation mistake.

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srishti  (5 years ago)

8C2*5C1 / 13C3 = 70/143

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