In a 100m race, Sam beats John by 5 seconds. On the contrary, if Sam allowed John to start 15m ahead of Sam, then Sam and John reach the finishing point at the same time. How long does Sam take to run the 100m race?
Choose the correct choice from the following answers
A) 4 seconds B) 25 seconds C) 29 seconds D) 21 seconds E) 17 seconds
Their difference is 5 second but this difference is 0 if john allows Sam to start the race from 15m ahead . that means Jhon was 15m away from finishing line when they started together . so He will cover 15 m in 5 seconds . so his speed =15/5= 
<gadget id="calculator">15/5</gadget>
<output>3</output>
3 metre / second . so time taken=100/5= 
<gadget id="calculator">100/5</gadget>
<output>20</output>
20 seconds . so Sam took= 17 seconds .   correct answer = 17 seconds
<result>E</result>
In a 100m race, Sam beats John by 5 seconds. On the contrary, if Sam allowed John to start 15m ahead of Sam, then Sam and John reach the finishing point at the same time. How long does Sam take to run the 100m race?