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1) A train passes a station platform in 36 seconds and a man standing on the platform in 20 seconds. If the speed of the train is 72 km/hr, what is the length of the platform?A) 375 B) 390 C) 40 D) 420
Answer & Explanation
Answer: 420 (Speed = 72 x 5 /18m/sec = 20 m/sec.
Length of the train = (20 x 20)m = 400 m.
Let the length of the platform be x metres.
Then, (x + 400)/36 = 20
x + 300 = 720
x = 420 m.
)
2) Two, trains, one from Pavonia to Virginia street and the other from Virginia to Pavonia, start simultaneously. After they meet, the trains reach their destinations after 16 hours and 25 hours respectively. The ratio of their speeds is:A) 2:5 B) 1:5 C) 4:5 D) 3:5
Answer & Explanation
Answer: 4:5 (Let us name the trains as A and B. Then,
(A's speed) : (B's speed) = a : b = 16 :25 = 4 : 5.
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3) A train overtakes two persons walking along a railway track. The first one walks at 5.4 km/hr. The other one walks at 7.2 km/hr. The train needs 8.4 and 8.5 seconds respectively to overtake them. What is the speed of the train if both the persons are walking in the same direction as the train?A) 158.4 km/hr B) 158.4 m/sec C) 40 m/sec D) 44 km/hr
Answer & Explanation
Answer: 158.4 km/hr (5.4 km/hr = 5.4 x 5 /18 m/sec = 1.5 m/sec
7.2 km/hr = 7.2 x 5 /18 m/sec = 2 m/sec.
Let the speed of the train be x m/sec.
Then, (x - 1.5) x 8.4 = (x - 2) x 8.5
8.4x - 12.6 = 8.5x - 17
0.1x = 4.4
x = 44
Speed of the train = 44 x 18/5 km/hr = 158.4 km/hr.
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4) Two trains are running at 30 km/hr and 20 km/hr respectively in the same direction. Fast train completely passes a man sitting in the slower train in 5 seconds. What is the length of the fast train?A) 25/9 B) 100/9 C) 125/9 D) 250/9
Answer & Explanation
Answer: 125/9 (Relative speed = (30 - 20) km/hr = 10 x 5/18 m/sec = 25/9 m/sec.
Length of faster train = 25/9 x 5 m = 125/9 m
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5) A train 900 metres long is running at a speed of 72 km/hr. If it crosses a tunnel in 1 minute, then the length of the tunnel (in meters) is:A) 300 B) 275 C) 280 D) 315
Answer & Explanation
Answer: 300 (Speed = 72 x 5/18 m/sec = 20 m/sec. Time = 1 minute = 60 seconds.
Let the length of the tunnel be x metres.
Then, (900 + x)/60 = 20
(900 + x) = 1200
x = 300 m)
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