Answer :

Solution :

Given : P and Q have speed 3x and 4x respectively.
P has already covered 140 m at the time of starting of the race.

Distance = Speed ×Time
Distance covered by P is 3x × t = 360 m
xt = 120 m
Distance covered by Q is 4x × t = 4 × 120 = 480 m
So, the distance between P and Q, when P wins the race = 500 m – 480 m = 20 m
Hence, the correct option is (A).