Probability word problem

Question

Emily's family goes to the dog park every 30 days. she has soccer practice every 9 days. she has both activities this Saturday. in how many days will she have both activities again?

Answer 1

Assuming both start at day 1, we need to know when they will both meet again. In other words, we need to find the Lowest Common Multiple of 9 and 30, that is:

Multiples of 9: 9 18 27 36 45 54 63 72 81 90

Multiples of 30: 30 60 90

So the LCM is 90.