Step by step
The question
Question: A car loan of $15000 at 6% for 5 years is paid monthly.
Find the monthly payment.
1 Read the numbers
P is the money borrowed: $15000.
r is the yearly rate: 6% is 0.06.
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.
0.06 divided by 12 is 0.005.
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 0.005 is 1.005.
4 Work it out
The top: 75.
With a calculator, 1.005 to the power negative 60 is about 0.741372.
1 minus that is 0.258628.
Now the top over the bottom.
75 divided by 0.258628 is 289.9920 and a bit.
Lenders round up to the next cent: $290 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 15000 times 0.005: $75.
The rest of the payment, $215, 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.