Problema Solution
Cory and Melissa are racing electronic cars around a circular track. They begin at the same time going in the same direction. Cory's car completes a revolution in 35 seconds, while Melissa's car completes a revolution in 30 seconds. How long will it take them before both cars reach the starting point again simultaneously?
Answer provided by our tutors
Since Cory takes 5 more seconds to complete a revolution than melissa, melissa gains 5 seconds on him every time. Thus, in 7 revolutions she will have gained a full 35 seconds (one of his revolutions) on him and they will meet at 7*30 = 210 seconds, when Melissa will have completed her 7th revolution and Coty will have completed his 6th revolution. This is the same as finding the least common multiple of 30 and 35.