Answer:
- 5 hours at 12 mph
- 4 hours at 15 mph
Explanation:
You want to know the travel times at 12 mph (going) and 15 mph (returning) for a round trip that took 9 hours.
Time and Speed
Over the same distance, the travel time is inversely proportional to the speed. This means ...
(time going)/(time returning) = 15/12 = 5/4 . . . . . . inverse of speed ratio
Then the fraction of total time spent on the trip to the cafe is ...
fraction of total spent "going" = 5/(5+4) = 5/9
And the time spent "going" is ...
(5/9)·(9 hours) = 5 hours
Anika traveled 5 hours at 12 mph, and 4 hours at 15 mph.
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Additional comment
The distance is the product of time and speed, so we see the distance in each direction is ...
(5 h)(12 mi/h) = 60 mi = (4 h)(15 mi/h)
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