Question

Excursion boat on the river takes 2 1/2 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 five times the rate of the river current what is the rate of the current

Answer 1

Let the current speed be "c";

Then the boat speed in still wate is "5c":

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Upstream speed:

distance = 12 miles ; rate = 5c-c = 4c mph ; time = 12/4c = 3/c hrs

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Downstream speed:

distance = 12 miles ; rate = 5c+c = 6c mph ; time = 12/6c = 2/c hrs

Explanation:

Equation:

time + time = 2 1/2 hrs

3/c + 2/c = 5/2

Multiply thru by 2c to get:

6 + 4 = 5c

c = 2 mph (speed of the current)

5c = 10 mph (speed of the boat in still water)