Step by step
The question
Question: A car loan of $28500 at 3.99% for 5 years is paid monthly.
Find the monthly payment.
1 Read the numbers
P is the money borrowed: $28500.
r is the yearly rate: 3.99% is 0.0399.
n is how many times a year: 12.
t is the time: 5 years.
2 Per payment
Interest is added each month.
The rate for one month is i: r over n.
0.0399 divided by 12 is 0.003325.
And N is how many payments: 12 times 5 is 60.
3 Use the formula
The payment each month: PMT = P times i, over 1 minus (1 + i) to the power negative N.
We put the numbers in: 1 plus 0.003325 is 1.003325.
4 Work it out
The top: 94.7625.
With a calculator, 1.003325 to the power negative 60 is about 0.819411.
1 minus that is 0.180589.
Now the top over the bottom.
94.7625 divided by 0.180589 is 524.7423 and a bit.
Lenders round up to the next cent: 524 dollars and 75 cents a month.
Careful!
That pays back only the loan.
The interest must be paid too.
5 Check
Let's check with the first month.
The interest that month is 28500 times 0.003325: 94 dollars and 76 cents.
The rest of the payment, 429 dollars and 99 cents, pays the loan down.
So the loan gets smaller every month.
It makes sense!
Let's look back.
First: read the numbers.
Then: per payment.
Then: use the formula.
Then: work it out.
Last: check.