The gym teacher buys basketballs every 5 years, soccer balls every 6, and baseballs every 7. If they bought all three this year, in how many years will they have to buy them all again?

210 years

Step-by-step explanation:

To find the solution to this problem, we need to find the lowest common multiple of these numbers. Hence, we need a number that can perfectly divide the numbers at the same time.

The lowest common multiples of these numbers is found to be 210.

In likewise manner, he will buy basketball and soccer together in the next 30 years, soccer and baseball together in the next 42 years and basketballs and baseballs in the next 35 years.