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 one:
A) 4 seconds B) 25 seconds C) 29 seconds D) 21 seconds E) 17 seconds

Rationale: "their difference is 5 second but this difference is 0 if john allows sam to start the race from 15 m ahead . that means jhon was 15 m away from finishing line when they started together . so he will cover 15 m in 5 seconds . so his speed = 15 / 5 = 3 metre / second . so time taken = 100 / 5 = 20 seconds . so sam took = 17 seconds . correct answer = e"
Answer: E