Two men A and B run a 500 m race, A having 140 m start, their speeds are as 3 : 4. Then, A wins by :

Here, A will have to cover a distance of (500 – 140) = 360 meters to reach the winning point while B 500 meters . A covers 3 while B covers 4.
∴ A covers 360 m while B covers 4 x 360/ 3 = 480 m
Hence, B will be (500 – 480) = 20 m behind the winning post.
∴ A wins by 20 m.