Lucy is expected to be charged by the interest amount of
in a month.
Explanation:
The simple interest is the interest that is charged on loan amounts or any other payments made which are lapsed for certain time duration.
The simple interest
on the principal amount
at rate percentage
for time duration of
years is calculated by the formula as shown below.
The typical balance on Lucy’s credit card is
so the interest has to be charged on this value only. Hence, the principal amount is
.
There are 12 months in a year so if the interest is charged as per month basis, the time of one month is taken as
years.
Substitute 650 for
, \frac{1}{12} for
and 18 for
to obtain the interest charged at a rate of 18% per annum.

Thus, the interest charged at Lucy’s credit card is
per month.
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Answer Details:
Grade: Middle School
Subject: Mathematics
Chapter: Simple Interest
Keywords: simple interest, interest, rate, time duration, months, years, rate percentage, principal, amount, credit card, Lucy.