In a given river, the current is 6 mph. A certain riverboat can travel 18 mph in still water. How far upstream (against the current) can the boat travel if a round trip is to take 10 hours?
A) 24
B) 48
C) 60
D) 80
E) 96
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knight247
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Upstream speed=12mph ....(18-6)
Downstream speed=24 mph .....(18+6)
The distance traveled in the upstream journey is the same as the distance traveled in the downstream journey.
Upstream travel time = Distance/12
Downstream travel time = Distance/24
Upstream travel time+Downstream travel time=10 hrs so we have
Distance/12+Distance/24=10
Distance=80 Hence D
Downstream speed=24 mph .....(18+6)
The distance traveled in the upstream journey is the same as the distance traveled in the downstream journey.
Upstream travel time = Distance/12
Downstream travel time = Distance/24
Upstream travel time+Downstream travel time=10 hrs so we have
Distance/12+Distance/24=10
Distance=80 Hence D
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Rate upstream = 18-6 = 12 miles per hour.mehrasa wrote:In a given river, the current is 6 mph. A certain riverboat can travel 18 mph in still water. How far upstream (against the current) can the boat travel if a round trip is to take 10 hours?
A) 24
B) 48
C) 60
D) 80
E) 96
Rate downstream = 18+6 = 24 miles per hour.
We can plug in the answers, which represent the distance.
Answer choice C: 60 miles.
Time upstream = 60/12 = 5 hours.
Time downstream = 60/24 = 15/6 hours.
Total time = 5 + 15/6 = 45/6 = 7.5 hours.
The time needs to increase by 1/3:
7.5 + (1/3)(7.5) = 10.
Thus, the distance must increase by 1/3:
60 + (1/3)60 = 80.
The correct answer is D.
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Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
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