Tuesday, November 12, 2013

given a loan on $6000, interest is 2%, how much would have to be paid monthly in order to pay off the loan?i know the question is really simple,...

The principal (P) is $6000 and the interest rate (r) is
0.02.


Now if the loan was for 1 month we would
have


`L=P(1+r)` or
`P=L/(1+r)`


If the loan was for 2 months we would
have


`(1+r)((1+r)P-L)=L` or  `(1+r)^2P-(1+r)L=L` which
gives `P=L/(1+r)+L/(1+r)^2`


So if the loan is n months we
would have


`P = sum_(j=1)^n L/(1+r)^j=L sum_(j=1)^n
1/(1+r)^n`


We can solve this by noting
that


`(1+r)P=L sum_(j=0)^(n-1)
1/(1+r)^n`


So


`(1+r)P - P = rP
= L(1-1/(1+r)^n)`


So
`L=(rP)/(1-1/(1+r)^n)`


Substituting P = $6000, r = 0.02 and
n = 24


`L =
(0.02(6000))/(1-1/(1-0.02)^24)`

Evaluating we get $317.23
per month.  Now this does seem high since 6000/24=250 but 2% per month is 48% for the
entire loan, so this is actually a high interest rate made more attractive by stating it
as a monthly interest rate.


So the final answer is $317.23
will pay off the loan in 24 months.

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