2026 · Q14
Had I walked 0.5 km/hr faster, I would have taken 8 minutes less to walk 2 km. What is my original speed?
Elementary MathematicsTime, Speed and Distance
- A2.5 km/hr
- B2.75 km/hr
- C3 km/hr
- D3.25 km/hr
Explanation
Let the original speed be v km/h. The time saved is 2/v − 2/(v + 0.5) = 8/60 = 2/15 hours. Simplifying, 2·0.5/[v(v + 0.5)] = 2/15, i.e. 1/(v² + 0.5v) = 2/15, so v² + 0.5v = 7.5. Solving v² + 0.5v − 7.5 = 0 gives v = 2.5 (the negative root −3 is rejected), option A.