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Answer : 2 4 kmph Explanation : Answer: B) 4 kmph Explanation: Let the distance in one direction = k kmsSpeed in still water = 4.5 kmphSpeed of river = 1.5Hence, speed in upstream = 4.5 - 1.5 = 3 kmphSpeed in downstream = 4.5 1.5 = 6 kmphTime taken by Rajesh to row upwards = k/3 hrsTime taken by Rajesh to row downwards = k/6 hrsNow, required Average speed =Total distanceTotal speed = 2kk3   k6 = 2k x 186k   3k = 4 kmph  Therefore, the average speed of the whole journey = 4kmph.

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