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It took 9 hours longer to go there than it did to come back. The average speed on the trip there was 10 km/h. The average speed on the way back was 55 km/h. How many hours did trip there take.
Let t = time to come back
(t+9) = time to got there
The two trip were the same distance, write a distance equation from this fact:
Dist = speed * time
to dist = from dist
10(t+9) = 55t
10t + 90 = 55t
90 = 55t - 10t
90 = 45t
t = 2 hrs to return, and 11 hrs to go
Check solution, find the distances
11*10 = 110 km
2*55 = 110 km