In a 200m race, if A gives B a start of 25 metres, then A wins the race by 10 seconds. Alternatively, if A gives B a start of 45 metres the race ends in a dead heat. How long does A take to run 200m? Pick:	A) 100 seconds	B) 112.5 seconds	C) 77.5 seconds	D) 87.5 seconds	E) None
Explanatory Answer   A gives B a start of 25 metres and still wins the race by 10 seconds.   Alternatively, if A gives B a start of 45 metres, then the race ends in a dead heat.   Therefore, the additional 20 metres start given to B compensates for the 10 seconds.   i.e., B runs 20 metres in 10 seconds.   Hence, B will take 100 seconds to run 200 metres.   We know that A gives B a start of 45 metres. B will take 22.5 seconds to run this 45 metres as B runs 20 metres in 10 seconds or at the speed of 2 m/s.   Hence, A will take 22.5 seconds lesser than B or   100 - 22.5= 
<gadget id="calculator">  100 - 22.5</gadget>
<output>77.5</output>
77.5 seconds to complete the race.   Answer 77.5 seconds
<result>C</result>
In a 200m race, if A gives B a start of 25 metres, then A wins the race by 10 seconds. Alternatively, if A gives B a start of 45 metres the race ends in a dead heat. How long does A take to run 200m?