A train covers 3 equal distances at speeds in the ratio 4:5:6. What is the ratio of the average speed over the entire journey to the lowest speed?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 45:37.
Let each distance = d
Speeds are 4k, 5k, and 6k
Total time = d/(4k) + d/(5k) + d/(6k) = (d/k)(1/4 + 1/5 + 1/6) = d/k × 37/60.
Average speed = 3d/[(d/k) × (37/60)] = 180k/37
Lowest speed = 4k
Ratio (Average : Lowest) = (180k/37) : 4k = 180 : 148 = 45 : 37