A delivery van moving at 36 km/h covers a sector path in 10 hours. At what speed must it travel to cover the same path distance in 8 hours? MCQ with Answer and Explanation
A carriage driving in a fog passed a man who was walking at the rate of 3 km/h in the same direction. He could see the carriage for 4 minutes and it was visible to him up to a distance of 100 meters. What is the speed of the carriage?
Explanation:
Time = 4 minutes = 4/60 = 1/15 hour. Distance = 100 meters = 0.1 km. Relative speed = Distance / Time = 0.1 / (1/15) = 1.5 km/h. Since the carriage moves in the same direction, Relative Speed = Speed of carriage - Speed of man => 1.5 = Speed of carriage - 3 => Speed of carriage = 4.5 km/h.
A motorboat covers a certain distance downstream in 4 hours and covers the same distance upstream in 5 hours. If the speed of the stream is 2 km/h, find the speed of the motorboat in still water.
Explanation:
Let speed of boat in still water be v. Downstream speed = v + 2, Upstream speed = v - 4. Distance is same, so 4(v + 2) = 5(v - 2) => 4v + 8 = 5v - 10 => v = 18 km/h.
A stream flows at 3 km/h. A boat can row 9 km/h in still water. How much time does it take to go 24 km downstream and return upstream to the starting point?
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