In a 100m race, Sam beats John by 4 seconds. On the contrary, if Sam allowed John to start 24m 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?
Choices.
A) 4 seconds
B) 25 seconds
C) 19 seconds
D) 21 seconds
E) 6.25 seconds

Rationale: "their difference is 4 second but this difference is 0 if john allows sam to start the race from 24 m ahead . that means jhon was 24 m away from finishing line when they started together . so he will cover 24 m in 4 seconds . so his speed = 24 / 4 = 6 metre / second . so time taken = 100 / 4 = 25 seconds . so sam took = 19 seconds . correct answer = c"
Answer: C