A, B and C are the three contestants in one km race. If A can give B a start of 40 metres and A can give C a start of 64 metres. How many metres start can B give C?

None of these

20 m

25 m

35 m

Explanation:

While A covers 1000 m, B covers $\left(1000-40\right)$=960 m and C covers $\left(1000-64\right)$=936 m

i.e., when B covers 960 m, C covers 936 m

$\text{When B covers 1000 m, C covers }\dfrac{936}{960} \times 1000\text{ = 975 m}$

i.e., B can give C a start of $\left(1000-975\right)$ = 25 m