SOLUTION: The excursion boat on the river takes 2½ hours to make the trip to a point 12 miles upstream and to return. If the rate at which the boat travels in still water is 5 times the rate

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Question 320479: The excursion boat on the river takes 2½ hours to make the trip to a point 12 miles upstream and to return. If the rate at which the boat travels in still water is 5 times the rate of the river current, what is the rate of the current?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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The excursion boat on the river takes 2½ hours to make the trip to a point 12 miles upstream and to return.
If the rate at which the boat travels in still water is 5 times the rate of the
river current, what is the rate of the current?
:
let x = rate of the current
and
5x = rate of the boat in still water
then
5x - x = 4x; effective rate upstream
and
5x + x = 6x; effective rate downstream
:
write a time equation, time = dist/speed
:
Upstream time + downstream time = 2.5 hrs
12%2F4x + 12%2F6x = 2.5 hrs
reduce fractions
3%2Fx + 2%2Fx = 2.5
5%2Fx = 2.5
5 = 2.5x
x = 5%2F2.5
x = 2 mph is the rate of the current
:
:
Check solution find the times; boat rate 2(5) = 10 mph
12/8 = 1.5 hr
12/12 = 1 hr
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total: 2.5 hr