How to determine credit card interest? I’m not sure how to use the example provided in my math book. It just does not seem to work for me.

Book example:

Previous Balance: $150.00

Minimum payment: $10.00

Interest per-annum: 18.6% (compounded daily)

= 142.19

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First off, if I enter that in my calculator I receive a syntax error; with or without the (365 x 1/12)

Second, if I use my own formula I receive a different answer:

1. 0.186 ÷ 12 = 0.0155 (Monthly Rate)

2. 0.0155 x 140 = 2.17 (different then the 2.19 shown in the example)

Please clarify!