Question

a credit card issuer charges an apr of 10.82%, and its billing cycle is 30 days long. what is its periodic interest rate?

Answer 1

how you get the periodic interest rate ?

Answer 2

the apr of 10.82% tells you that 10.82% is charged **per year**

however, it wants the periodic interest rate (which is based on the billing cycle, 30 days)

what fraction of one year is 30 days? once you have that fraction, multiply that by the apr to get the 30-day interest rate.