one car can travel around the track in 10 seconds and the ot

one car can travel around the track in 10 seconds and the other car in 15 seconds. if both cars start from the same place how long will it take for them to meet at the same place if they continue to race.

Solution

Since they must meet at the starting line together then car 1 does laps of 10, 20 30 sec. Car 2 does laps of 15, 30, 45.
So 30 sec after the start they meet again at the same place.