Question

A motorboat, that has speed of 10 km hour in still water, left a pier traveling against the current of the river. Forty-five minutes after the boat left the pier, the motor of the boat broke, and the boat began drifting with the current. After three hours of drifting with the current, the boat was back at the pier where it had started. What is the speed of the current of the river?

Answer 1

9514 1404 393

Answer:

  2 km/h

Step-by-step explanation:

  distance = speed × time

The boat's progress upriver can be modeled by ...

  (10 -c)(3/4) +(0 -c)(3) = 0

  7.5 -3.75c = 0 . . . . simplify

  2 -c = 0 . . . . . . . . . divide by 3.75

  c = 2 . . . . . . add c

The speed of the current is 2 km per hour.