Question: A and B together can complete a work in 12 days. A alone can complete it in 20 days. If B does the work only for half a day daily, then in how many days A and B together will complete the work?
Options:
(A) 65 days
(B) 85 days
(C) 15 days
(D) 45 days
(E) 13 days
Ans: (C)
CoT: B's 1 day work = (1/12 - 1/20) = 1/30
Now, (A + B)'s 1 day work = (1/20 + 1/60) = 1/15
So, A and B together will complete the work in 15 days.
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Question: Find the probability that the number drawn is a factor of 50.
Options:
(A) 1/25
(B) 1/50
(C) 3/25
(D) 3/50
(E) 7/50
Ans: (D)
CoT: The factors of 50 are 1, 2, 5, 10, 25, 50
Therefore, required probability = 6/100 = 3/50.
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Question: A train running at the speed of 60 km/hr crosses a pole in 9 sec. What is the length of the train?
Options:
(A) 287
(B) 699
(C) 677
(D) 168
(E) 150
Ans: (E)
CoT: Speed = 60 * 5/18 = 50/3 m/sec
Length of the train = speed * time = 50/3 * 9 = 150 m
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