X and Y run a 100m race,where X beats Y by 20 m. To do a favor to Y, X starts 10m behind the starting line in a second 100m race. Both run at the same previous speed. Which of the following is true?
Answers.
A) X Beats Y by 2m  B) X Beats Y by 0.5 m  C) X Beats Y by 4 m  D) X Beats Y by 4 m  E) Y Beats X by 10m
Let's suppose that the speed of X is 10m/s and that the speed of Y is 8 m/s.   So, in the first race, the results are the following:   X crosses the finish line in 10s. In other words, X has run 100m in 10 s.   In 10s, Y has run 80 meters.   Therefore, there is the difference of 20 meters mentioned in the question.   Now, let's review the second race.   In 12 seconds, X can complete the 100 meters race. We have to remember that X is 4 meters behind the starting line.   But in 12 seconds, Y has covered (96 ) =96 meters. Also, it is important to notice that in 12 seconds Y cannot arrive to the finish line.   So, 100 - 96 = 4 meter   Answer: X Beats Y by 4 m
<result>D</result>
X and Y run a 100m race,where X beats Y by 20 m. To do a favor to Y, X starts 10m behind the starting line in a second 100m race. Both run at the same previous speed. Which of the following is true?