SOLUTION: A car travels 40km per hour between two cities that are 90 km apart. How fast must the car travel on the return trip to average 50 km per hour for the round-trip?

Question 203250: A car travels 40km per hour between two cities that are 90 km apart. How fast must the car travel on the return trip to average 50 km per hour for the round-trip?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
A car travels 40km per hour between two cities that are 90 km apart.
How fast must the car travel on the return trip to average 50 km per hour,
for the round-trip?
:
Let s = speed required on the return trip to average 50 km/h
:
Write a time equation Time =
:
outbound time + return time = time at 50 km/hr
+ =
Multiply by 200s:
200s* + 200s* = 200s*
Cancel out the denominators:
5s(90) + 200(90) = 4s(180)
:
450s + 18000 = 720s
:
18000 = 720s - 450s
:
18000 = 270s
s =
s = 66 km/hr required on the return trip
:
:
Check solution in the time equation
+ =
2.25 + 1.35 = 3.6

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