SOLUTION: Hi the distance between 2 towns is 90km. A driver averages 30km per hour in one direction and 45km per hour on the return. Calculate the total time and average speed of journey.my

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Question 1079966: Hi
the distance between 2 towns is 90km. A driver averages 30km per hour in one direction and 45km per hour on the return. Calculate the total time and average speed of journey.my answer is 2.5 hours and 36km per hour. Textbook says 5 hours and 36km per hour. Who is correct?
Thanks
Answer by ikleyn(52797) About Me  (Show Source):
You can put this solution on YOUR website!
.
Total time for journey in one direction and back is

90%2F30+%2B+90%2F45 = 3 + 2 = 5 hours.


The average speed of the journey in both directions is 

%2890%2B90%29%2F5 = 180%2F5 = 36 km per hour.

The lesson to learn from this solution: 
     The average speed is the total distance divided by the total time.