A man travels the first 120 km of his journey at 40 km/hr. On a clear highway, he travels the next 120 km at 60 km/hr. What is his average speed for these 240 km?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 48 km/hr
Average speed = total distance ÷ total time. It is not the simple average of 40 and 60, because the man spends more time on the slower part.
Time for the first 120 km \(\displaystyle =\frac{120}{40}=3\) hr
Time for the next 120 km \(\displaystyle =\frac{120}{60}=2\) hr
Total time \(=3+2=5\) hr
Average speed \(\displaystyle =\frac{240}{5}=48\) km/hr