2012 · Q5
A train travels at a certain average speed for a distance of 63 km. Thereafter it travels a distance of 72 km with an average speed of 6 km/hour more than the original speed. Total time taken to complete the journey is 3 hours. What is the original average speed of the train ?
General Mental Ability, Quantitative Aptitude and StatisticsTime, work and measurement
- A36 km/hour
- B42 km/hour
- C48 km/hour
- D54 km/hour
Explanation
Let the original speed be x km/h; then 63/x + 72/(x + 6) = 3. Substituting x = 42 gives 63/42 = 1.5 hours for the first leg and 72/48 = 1.5 hours for the second, totalling exactly 3 hours. None of the other options satisfies the equation — for example, x = 36 gives about 3.46 hours. Hence the original average speed is 42 km/h.