In a 500 m race,the ratio of the speeds of two contestants A and B is 3 : 4. A has a start of 140 m.Then,A wins by	Choose the correct choice
A) 60 m	B) 40 m	C) 20 m	D) 10 m	E) 50 m

Rationale: "solution to reach the winning post a will have to cover a distance of ( 500 - 140 ) m , i . e , 360 m . while a covers 3 m , b covers 4 m . while a covers 360 m , b covers ( 4 / 3 x 360 ) m = 480 m thus , when a reaches the winning post , b covers 480 m and therefore remains 20 m behind . ∴ a wins by 20 m . answer c"
Answer: C