2022 · Q19
A car travels from A to B at a speed of 40 km/hr, travels back from B to A at a speed of 30 km/hr and again goes from A to B at a speed of 60 km/hr. What is the average speed of the car?
Elementary MathematicsTime, Speed and Distance
- A130/3 km/hr
- B42 km/hr
- C40 km/hr
- D125/3 km/hr
Explanation
Average speed = total distance / total time = 3d/(d/40+d/30+d/60) = 3d/(9d/120) = 40 km/hr. The plain arithmetic mean of the speeds (130/3) is the common distractor. Hence the keyed option is C.