जॉइन Examsbookउत्तर : 2. "4 kmph"
Rajesh rows in still water with a speed of 4.5 kmph to go to a certain place and comes back. Find his average speed for the whole journey, if the river is flowing with a speed of 1.5 kmph?5
प्र: Rajesh rows in still water with a speed of 4.5 kmph to go to a certain place and comes back. Find his average speed for the whole journey, if the river is flowing with a speed of 1.5 kmph?
- 12 kmphfalse
- 24 kmphtrue
- 36 kmphfalse
- 48 kmphfalse
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उत्तर : 2. "4 kmph"
व्याख्या :
Answer: B) 4 kmph Explanation: Let the distance in one direction = k kms Speed in still water = 4.5 kmph Speed of river = 1.5 Hence, speed in upstream = 4.5 - 1.5 = 3 kmph Speed in downstream = 4.5 + 1.5 = 6 kmph Time taken by Rajesh to row upwards = k/3 hrs Time taken by Rajesh to row downwards = k/6 hrs Now, required Average speed =Total distanceTotal speed = 2kk3 + k6 = 2k x 186k + 3k = 4 kmph Therefore, the average speed of the whole journey = 4kmph.