Two runners start running at the same time from the start/finish line of a 400 meter oval track. One runner run laps of 1 minute 15 seconds and the other runs laps of 1 minute 45 seconds. How long will it be before the runners cross the start/finish line at the same time?
First runner ==60 + 15 ==75 seconds per lap
2nd runner ==60 + 45 ==105 seconds per lap
LCM[75, 105] ==525
First runner==525 / 75 == 7 laps
2nd runner==525 / 105== 5 laps
So, it will be: 525 seconds ==8 minutes and 45 seconds - when they will cross the finish line at the same time.
