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Q47 (CDS-II/2012) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Quantitative aptitude topics Answer Verified

A bus travels at a speed of 50 km per hour to go from its origin to its destination at a distance of 300 km and travels at a speed of 60 km per hour to return to the origin. What is the average speed of the bus?

Result
Your answer: —  Â·  Correct: A
Explanation

The average speed of an object is defined as the total distance covered divided by the total time taken [1]. In this scenario, the bus travels a distance of 300 km at 50 km/h and returns the same 300 km at 60 km/h. The time taken for the onward journey is 6 hours (300/50), and the return journey takes 5 hours (300/60). The total distance is 600 km, and the total time is 11 hours. Thus, the average speed is 600/11, which equals approximately 54.5454... km/h, rounded to 54.55 km/h. Alternatively, when distances are equal, the average speed is the harmonic mean of the speeds: (2 * v1 * v2) / (v1 + v2). Substituting the values: (2 * 50 * 60) / (50 + 60) = 6000 / 110 = 54.55 km/h.

Sources

  1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 8: Measurement of Time and Motion > 8.3 Speed > p. 113
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