question: A train running at the speed of 60 km/hr crosses a pole in 15 sec. What is the length of the train?
Options:
(A) 120 m
(B) 190 m
(C) 115 m
(D) 110 m
(E) 250 m
answer: Stream of consciousness: Speed = 60 * 5/18 = 50/3 m/sec
Length of the train = speed * time = 50/3 * 15 = 250 m The answer is (E).
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question: The average of 11 results is 50, if the average of first six results is 49 and that of the last six is 52. Find the sixth result?
Options:
(A) 22
(B) 56
(C) 44
(D) 55
(E) 81
answer: Stream of consciousness: 1 to 11 = 11 * 50 = 550
1 to 6 = 6 * 49 = 294
6 to 11 = 6 * 52 = 312
6th = 294 + 312 550 = 56 The answer is (B).
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question: A man rows his boat 85 km downstream and 45 km upstream, taking 2 1/2 hours each time. Find the speed of the stream?
Options:
(A) 5 kmph
(B) 6 kmph
(C) 7 kmph
(D) 8 kmph
(E) 9 kmph
answer: Stream of consciousness: Speed downstream = d/t = 85/(2 1/2) = 34 kmph
Speed upstream = d/t = 45/(2 1/2) = 18 kmph
The speed of the stream = (34 - 18)/2 = 8 kmph The answer is (D).
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question: Twelve coins are tossed simultaneously. In how many of the outcomes will the third coin turn up a head?
Options:
(A) 2^9
(B) 2^11
(C) 3 * 2^8
(D) 3 * 2^9
(E) 3 * 2^10
answer:
Stream of consciousness: Fix the third coin as H. The remaining 11 coins have 2^11 outcomes. The answer is (B).
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