2022 · Q39
X takes 3 hours longer than Y to walk 30 km. If X doubles his speed, he takes 2 hours less than Y. What is the speed of Y?
Elementary MathematicsTime, Speed and Distance
- A3 km/hr
- B4km/hr
- C42/7 km/hr
- D43/7 km/hr
Explanation
30/u − 30/v = 3 and 30/v − 30/(2u) = 2. From the second, 30/v = 2+15/u; substituting into the first gives 15/u = 5, so u = 3, and then 30/v = 7, i.e. v = 30/7 = 42/7 km/h. The keyed option is C.