In a 100 m race, A covers the distance in 36 seconds and B in 45 seconds. IN this A beats B by

A: 20 m

B: 24 m
C: 28 m

D: 30 m

In $100$ meters race, A covers the distance in $36$ seconds and B in $45$ seconds. Clearly, A beats B by $(45-36)=9$ seconds.

Speed of B $=\frac{100}{45}$ m/s

Distance covered by B in $9$ seconds $=\frac{100}{45}\times 9$ $=20$ meters.

That is A beat B by $20$ meters.