2015 · Q27
With a uniform speed, a car covers a distance in 8 hours. Had the speed been increased by 4 km/hr, the same distance could have been covered in 7 hours and 30 minutes. What is the distance covered?
Elementary MathematicsTime, Speed and Distance
- A420 km
- B480 km
- C520 km
- D640 km
Explanation
This is a distance = speed × time setup with two scenarios for the same distance. Let the speed be v km/h: then 8v = 7.5(v + 4). Solving: 0.5v = 30, so v = 60 km/h, and the distance is 8 × 60 = 480 km. Checking: at 64 km/h for 7.5 h the car also covers 480 km. Option (a) 420 km comes from arithmetic slips in solving the equation. Hence option (b).