Ramesh covers one-fourth of the total distance at 30 km/hr, one-fourth at 20 km/hr and the rest of his journey at 60 km/hr. Find Ramesh's average speed for the whole distance?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 34.28 km/hr
Average speed = total distance ÷ total time, not the average of the three speeds, because Ramesh spends different lengths of time at each speed.
Assuming the total distance to be 240 km:
First quarter, 60 km at 30 km/hr: 2 hr
Second quarter, 60 km at 20 km/hr: 3 hr
The remaining half, 120 km at 60 km/hr: 2 hr
Total time \(=2+3+2=7\) hr
Average speed \(\displaystyle =\frac{240}{7}=34.28\ldots\) km/hr