A train passes a pedestrian standing on a platform in 8 seconds and passes the platform itself, which is 200 meters long, in 18 seconds. Find the speed of the train in km/h. MCQ with Answer and Explanation
A train passes a pedestrian standing on a platform in 8 seconds and passes the platform itself, which is 200 meters long, in 18 seconds. Find the speed of the train in km/h.
A. 84 km/h
B. 80 km/h
C. 64 km/h
D. 72 km/h
Answer: Option D
Solution (By JKSSB Mock Tests)
Time taken to cross the platform alone = 18 - 8 = 10 seconds. Speed of train = 200 / 10 = 20 m/s. In km/h = 20 * (18/5) = 72 km/h.
Explanation:
Upstream speed = 24 / 4 = 6 km/h. Upstream Speed = Speed in still water - Current speed => 6 = Speed in still water - 2 => Speed in still water = 8 km/h.
A boat can row 15 km/h in still water. If the velocity index of the stream tracks at 3 km/h, find the time parameter taken by the boat to row 36 km upstream.
Explanation:
Let original speed be s. 240 / s - 240 / (s + 10) = 1 => 240(10) = s(s + 10) => 2400 = s(s + 10). Solving s^2 + 10s - 2400 = 0 gives (s - 40)(s + 50) = 0. Since speed is positive, s = 40 km/h.
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