A runs twice as fast as B and gives B a start of 71m.How long should the racecourse be so that A and B might reach in the same time?  Pick:
A) 75 m .	B) 80 m .	C) 150 m .	D) 142 m .	E) none of the above

Rationale: "ratio of speeds of a and b is 2 : 1 b is 71 m away from a but we know that a covers 1 meter ( 2 - 1 ) more in every second than b the time taken for a to cover 71 m is 71 / 1 = 71 m so the total time taken by a and b to reach = 2 * 71 = 142 m answer : d"
Answer: D