In a 500 m race, the ratio of the speeds of two contestants A and B is 3 : 4. A has a start of 155 m. Then, A wins by:
Pick:	A) 60 m	B) 20 m	C) 40 m	D) 20 m	E) 23 m

Rationale: "to reach the winning post a will have to cover a distance of ( 500 - 155 ) m , i . e . , 345 m . while a covers 3 m , b covers 4 m . while a covers 345 m , b covers 4 x 345 / 3 m = 460 m . thus , when a reaches the winning post , b covers 460 m and therefore remains 40 m behind . a wins by 40 m . answer : c"
Answer: C