Tom goes to the library every 4th day, Terry goes every 6th day, which day will both go on same day?

Question

Which day will both boys go to the library on the same day? 

Answer 1

Tom goes every 4th day.   This means he goes on day 4, 8, 12, ....

Terry does every 6th day.  This means he goes on day 6, 12, ...

 

Notice that they are both on the 12th day and as long this continues will always be together at the library every 12th day.