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? Options:
A) 100 seconds
B) 112.5 seconds
C) 77.5 seconds
D) 87.5 seconds
E) none

Rationale: 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 = 77.5 seconds to complete the race . answer c
Answer: C