SOLUTION: a motorboat leaves a harbor and travels at an average speed of 15 mph toward an island. The average speed on the return trip was 10 mph. how far was the island from the harbor if t

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Question 985826: a motorboat leaves a harbor and travels at an average speed of 15 mph toward an island. The average speed on the return trip was 10 mph. how far was the island from the harbor if the total trip took 5 hours?
Answer by ikleyn(52852) About Me  (Show Source):
You can put this solution on YOUR website!
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Let  L  be the distance from the starting point to the ending point in miles.

Motorboat spent  L%2F15  hours for the way forward and  L%2F10  to return back.

In total,  it is  5  hours.  It gives you an equation

L%2F15 + L%2F10 = 5.

Solve it.  The common denominator is 30.

%282L%29%2F30 + %283L%29%2F30 = 5,

2L + 3L = 5*30,

5L = 150,

L = 150%2F5 = 30 miles.