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A man starts rowing from Point A in the direction of the water flow at

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Joined: 25 Dec 2018
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A man starts rowing from Point A in the direction of the water flow at  [#permalink]

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10 Mar 2019, 10:26
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Difficulty:

45% (medium)

Question Stats:

75% (04:23) correct 25% (03:47) wrong based on 8 sessions

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A man starts rowing from Point A in the direction of the water flow at a constant speed of 10 kilometers per hour. After rowing for 10 kilometers, he remembers that he forgot an important object at Point A and turns back to get it. After getting the object, he starts moving again in the direction of water flow, but due to an onset of exhaustion, he now rows at a constant speed of 8 kilometers per hour. After rowing for 26 kilometers, he reaches Point D, where he rests for 1 hour, and then resumes his journey in the same direction, rowing at a constant speed of 9 kilometers per hour, till he reaches Point B, which is 14 kilometers downstream from Point D. If the speed of water flow is 5 kilometers per hour, what is the average speed of the man for the entire journey?

A)9 kilometers per hour

B)13017 kilometers per hour

C)12017 kilometers per hour

D)203 kilometers per hour

E)6 kilometers per hour
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Re: A man starts rowing from Point A in the direction of the water flow at  [#permalink]

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10 Mar 2019, 10:38
1
Average Speed = Total Distance/Time taken
Total Distance = 10+10+26+14 = 60km
Time for first 10km = 10/10+5 = 40min or 2/3 hours (As the water is flowing in the direction of the boat)
Time for reverse 10km = 10/10-5 = 2hr
Time for 26km = 26/8+5 = 2hr
Time for 14km = 14/9+5 = 1hr
+1 hr of rest.

Average Speed = 60/6+(2/3) = 60*3/20 = 9 hours.

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Re: A man starts rowing from Point A in the direction of the water flow at   [#permalink] 10 Mar 2019, 10:38
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