A woman travels 250 km at a speed of 25 km/hr, second distance of 162 km at 27…
2025
A woman travels 250 km at a speed of 25 km/hr, second distance of 162 km at 27 km/hr
and a third distance of 272 km at 34 km/hr. Find her average speed for the whole
journey (in km/hr).
Answer: B. 28.5 — When a journey has several legs covered at different speeds, the average speed for the whole journey is the total distance covered divided by the total time…
- A.
34.6
- B.
28.5
- C.
37.5
- D.
29.3
Attempted by 32 students.
Show answer & explanation
Correct answer: B
When a journey has several legs covered at different speeds, the average speed for the whole journey is the total distance covered divided by the total time taken — it is NOT the arithmetic mean of the leg speeds. Because it is a distance-over-time ratio for the entire trip, the resulting average speed must always lie between the slowest and the fastest speed actually driven on any leg.
First leg: distance = 250 km, speed = 25 km/hr, so time taken = 250 divided by 25 = 10 hours.
Second leg: distance = 162 km, speed = 27 km/hr, so time taken = 162 divided by 27 = 6 hours.
Third leg: distance = 272 km, speed = 34 km/hr, so time taken = 272 divided by 34 = 8 hours.
Total distance covered = 250 + 162 + 272 = 684 km.
Total time taken = 10 + 6 + 8 = 24 hours.
Average speed for the whole journey = total distance divided by total time = 684 divided by 24 = 28.5 km/hr.
28.5 km/hr lies between the slowest leg speed of 25 km/hr and the fastest leg speed of 34 km/hr, as a valid average speed must. Checking the units confirms the method: km divided by hr gives km/hr, and 684 km over 24 hours indeed gives 28.5 km/hr.