SOLUTION: A boat can travel upstream at a rate of 6 mph and can travel at a rate of 12 mph going downstream. If the boat leaves at 7 am and must return at 2 pm, how far upstream can the boat

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Question 905792: A boat can travel upstream at a rate of 6 mph and can travel at a rate of 12 mph going downstream. If the boat leaves at 7 am and must return at 2 pm, how far upstream can the boat travel.

Found 2 solutions by Alan3354, richwmiller:
Answer by Alan3354(69443) (Show Source):
You can put this solution on YOUR website!
A boat can travel upstream at a rate of 6 mph and can travel at a rate of 12 mph going downstream. If the boat leaves at 7 am and must return at 2 pm, how far upstream can the boat travel.
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The avg speed of the round trip is 2*6*12/(6+12) = 8 mi/hr
In 7 hours he can go 7*8 = 56 miles
--> 28 miles each way

Answer by richwmiller(17219) (Show Source):
You can put this solution on YOUR website!
a+b=14-7=7
a+b=7
6*(7-b)=12*b
42-6b=12b
42=18b
42/18=b
b=7/3=2.333
a=7-b
a=21/3-7/3=14/3=4.67
a=14/3
b=7/3
6*a=7*b
6*14/3=84/3=28 miles
12*7/3=84/3=28 miles