q: A train traveling at 72 kmph crosses a platform in 30 seconds and a man standing on the platform in 16 seconds. What is the length of the platform in meters?
Options:
(A) 240 meters
(B) 360 meters
(C) 280 meters
(D) 600 meters
(E) Cannot be determined
a: Speed of the train in metres/sec = 72000/3600 = 20
Distance travelled by train to cross the platform = 30 * 20 = 600 = Length of train + Length of platform
Distance travelled by train to cross the man = 16 * 20 = 320 = Length of train
Length of platform = 600 - 320 = 280 The answer is (C).
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q: In what time will a railway train 60 m long moving at the rate of 36 kmph pass a telegraph post on its way?
Options:
(A) 10 sec
(B) 8 sec
(C) 5 sec
(D) 6 sec
(E) 11 sec
a: T = 60/36 * 18/5 = 6 sec The answer is (D).
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q: If the ratio of boys to girls in a class is B and the ratio of girls to boys is G; then 7 (B + G) is ?
Options:
(A) more than 7
(B) Less than 3
(C) More than 3
(D) Less than 1/3
(E) none of these
a: Let number of boys = x
Let number of girls = y
Therefore x/y = B and y/x = G
7(B + G) = 7[(x/y) + (y/x)] = 7[(x2 + y2)/xy] > 7 The answer is (A).
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q: Look at this series: 3, 4, 7, 8, 11, 12, ... What number should come next?
Options:
(A) 15
(B) 14
(C) 17
(D) 12
(E) 19
a:
This alternating addition series begins with 3; then 1 is added to give 4; then 3 is added to give 7; then 1 is added, and so on. The answer is (A).
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