Sam covers a total distance of 80km while travelling from a certain point X to a certain point Y and come back again to the start point X. He covers the first 40 km distance from point X to point Y at a speed of 25 km/hr. While travelling back to the point X from point Y, Sam drives his vehicle at a speed of 15 km/hr. Calculate the average speed of Sam for the entire journey.

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Your question is – Sam covers a total distance of 80km while travelling from a certain point X to a certain point Y and come back again to the start point X. He covers the first 40 km distance from point X to point Y at a speed of 25 km/hr. While travelling back to the point X from point Y, Sam drives his vehicle at a speed of 15 km/hr. Calculate the average speed of Sam for the entire journey.

I have solved this problem thus, you can read my Explanation for your better understanding:

We know the standard formula for speed, time and distance as, distance = speed * time.
Using this formula we can easily find out the correct answer to the above question.

According to the question,
Total distance covered by Sam = 80 km …..i
Speed of Sam while travelling from point X to point Y = 25 km/hr …..ii
∴ Time taken by Sam to go from point X to point Y = 40/25 = 1.6 hours …..iii
Speed of Sam while travelling back from point Y to point X = 15 km/hr …..iv
∴ Time taken by Sam to go from point Y to point X = 40/15 = 2.66 hours …..v
∴ The total time to cover the total distance of 80 km = 1.6 + 2.66 = 4.26 hours …..vi
∴ Average speed for the entire round trip = 80/4.26 = 18.77 km/hr

Thanks.