2015 · Q28
By increasing the speed of his car by 15 km/hour, a person covers 300 km distance by taking an hour less than before. The original speed of the car was
Elementary MathematicsTime, Speed and Distance
- A45 km/hour
- B50 km/hour
- C60 km/hour
- D75 km/hour
Explanation
300/v - 300/(v + 15) = 1 gives v^2 + 15v - 4500 = 0, i.e. (v + 75)(v - 60) = 0, so v = 60 km/h. Hence option (c).