If a firm pays it bills with a 30-day delay, what fraction of its purchases will be paid for in the current quarter? In the following quarter? What if its payment delay is 60-days?

Can anyone tell me how to start this? I'm sure it's an equation but I can't wrap my arms around where to even start.

There are 4 quarters in the year.

So if you don't pay until the next month... (30 day delay)

Then you only pay for 2 months out of 3... (3 months to a quarter x 4 quarters = 12 months)

So 1/3 of purchases in the quarter are not paid in the quarter at 30 days.

2/3 of purchases in the quarter are paid in this quarter at 30 days.

For 60, that just adds another month to the future.
So, this quarter 1/3, next quarter 2/3