Question 724084
Kate and Ian meet in the gym one evening, and that night Kate thinks:
I will go the gym again in 2 days,
and again 4 days from today,
and again 6 days from today,
and again 8 days from today,
and again 10 days from today,
and again 12 days from today, and so on.
One of those days, I may find Ian in the gym again.
 
At the same time Ian is thinking that he would not mind meeting Kate in the gym again.
He plans to go to the gym again in 3 days,
and again 6 days from today,
and again 9 days from today,
and again 12 days from today, and so on.
 
a. Kate and Ian will both attend the gym again on the same evening in 6 days, and then again 6 days later (12 days from today).
 
b. The times from today until future visits to the gym are multiples of 2 for Kate and multiples of 3 for Ian.
The times from today until their future visits to the gym coincide are multiples of 2 and multiples of 3, which makes them multiples of 2X3=6.