2019 · Q31
A race has three parts. The speed and time required to complete the individual parts for a runner is displayed on the following chart:
Part I: Speed 9 kmph, Time 50 minutes; Part II: Speed 8 kmph, Time 80 minutes; Part III: Speed 7.5 kmph, Time 100 minutes.
What is the average speed of this runner?
Elementary MathematicsTime, Speed and Distance
- A8.17 kmph
- B8.00 kmph
- C7.80 kmph
- D7.77 kmph
Explanation
Distances: 9×50/60 = 7.5 km, 8×80/60 = 32/3 km, 7.5×100/60 = 12.5 km; total 92/3 km in 230 min = 23/6 h. Average speed = (92/3)/(23/6) = 8.00 km/h.