A train 120 meters long passes a telegraph post in 8 seconds. How long will it take to pass a platform 240 meters long? MCQ with Answer and Explanation
A sound pulse takes 6 seconds to reach the ocean floor and bounce back to a submarine. If the speed of sound in water is 1480 m/s, find the depth of the ocean floor.
Explanation:
Relative speed = 100 / 6 = 50/3 m/s = (50/3) * (18/5) = 60 km/h. Since the train passes him from behind (same direction), Relative Speed = Speed of train - Speed of man => 60 = Speed of train - 5 => Speed of train = 65 km/h.
A person can row 10 km/h in still water. If it takes him exactly twice as long to row upstream as to row downstream over the same stretch, find the speed of the current.
Explanation:
Let speed of current be c km/h. Downstream speed = 10 + c, Upstream speed = 10 - c. Given: 2 * (10 - c) = 10 + c => 20 - 2c = 10 + c => 3c = 10 => c = 10/3 = 3.33 km/h.
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