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 one
A) 75 m.  B) 80 m.  C) 150 m.  D) 142 m.  E) None of the above
ratio of speeds of a and b is 2:1   b is 71m 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 71m is   71/1= 
<gadget id="calculator">  71/1</gadget>
<output>71</output>
71m   so the total time taken by a and b to reach=2*71= 
<gadget id="calculator">2*71</gadget>
<output>142</output>
142m   ANSWER:142 m.
<result>D</result>
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?