SOLUTION: Hello, I am having a hard time knowing how to set-up and solve this word problem: The Connecticut River flows at a rate of 4km/h for the length of a popular scenic route. In or

Question 865689: Hello, I am having a hard time knowing how to set-up and solve this word problem:
The Connecticut River flows at a rate of 4km/h for the length of a popular scenic route. In order for a cruiser to travel 60 km upriver and then return in a total of 8hr, how fast must the boat be able to travel in still water?
Thanks for your help!
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
The Connecticut River flows at a rate of 4km/h for the length of a popular scenic route. In order for a cruiser to travel 60 km upriver and then return in a total of 8hr, how fast must the boat be able to travel in still water?
***
let x=speed of boat in still water
x+4=speed of boat down river
x-4=speed of boat up river
travel time=distance/speed
..

LCD:(x-4)(x+4)
60(x+4)+60(x-4)=8(x+4)(x-4)
60x+240+60x-240=8(x^2-16)
120x=8x^2-128
8x^2-120x-128=0
x^2-15-16
(x-16)(x+1)=0
x=-1 (reject, x>0)
or
x=16
how fast must the boat be able to travel in still water? 16 km/h
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