The annual percentage rate on a credit card determines

The right answer is "The amount of interest you are charged on credit card purchases".

A credit card is a banking instrument that allows to carry out economic transactions of purchase to the credit of goods and services, with an available monetary limit, and paying a previously established amount of interests.

Interest is an index used to measure the cost or value of using a credit. When acquiring a credit card, the bank establishes previously what percentage of interest will be paid, this may vary according to the banking agency that provides the service.
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