On my way from the office to the Website class, I drive at 30 kmph and on the return journey I drive at 45 kmph. What is my average speed of travel?

Question: On my way from the office to the Website class, I drive at 30 kmph and on the return journey I drive at 45 kmph. What is my average speed of travel?

Solution:
Let the distance between the office and Website class be x km.

∴ Time taken on my onward journey = x/30 hours
and time taken on my return journey = x/45 hours

∴ The total time taken for my onward and return journey = x/30 + x/45 = 5x/90 hours.
The total distance traveled both ways = 2x km

∴ Average speed = 2x/(5x/90) = 36 kmph.