X, Y and Z are three contestants in a race of 1000 m. Assume that all run with different uniform speeds. X gives Y a start of 40 m and X gives Z a start of 64 m. If Y and Z were to compete in a race of 1000 m, how many metres start will Y give to Z?

Correct Answer: (B) 25

In the time X runs 1000 m, Y runs $1000 - 40 = 960$$\text{ m}$ and Z runs $1000 - 64 = 936$$\text{ m}$. In the time Y runs 960 m, Z runs 936 m, so when Y runs 1000 m, Z runs $1000$$\times$ $\frac{936}{960}$ = 975 $\text{ m}$. Therefore, Y can give Z a start of $1000 - 975 = 25$$\text{ metres}$.