Ok so I'm trying to finish my Pre-Calc project and I cannot figure out what I am doing wrong. Here is the problem: I have a student loan for $32,016. For loan 1, the interest rate is 5%. Loan 2 has an interest rate of 6.8%. I am putting $400 each month toward the loan and am trying to figure out how long it will take to pay off each loan. Can anyone figure out what I am doing wrong? Obviously loan 1 will be payed off quicker but I keep getting loan 2 as the quicker payoff. I attached the problem. Hopefully it comes out ok. Thanks for any help

loan problem.txt

For anyone dubious about downloading attachments from new members:

Length of time it will take to pay off loan if use LOAN 1: 

A=P(1+r/k)^kt

32,016=400(1+.05/12)12t

80.04=1.004212t

Log1.004280.04=12t

Log 80.04/ log 1.0042=12t

1045.65=12t

88 months=t

7 years, 4 months



Length of time it will take to pay off loan if use LOAN 2:

A=P(1+r/k)^kt

32,016=400(1+.068/12)12t

80.04=1.005712t

Log1.005780.04=12t

Log 80.04/ log 1.0057=12t

771.05=12t

64.25 months=t

5 years, 5 months

Edited October 9, 200817 yr by Sayonara³

Oh and btw its ^kt not multiplied kt. Didn't show up like that...

 

Thanks say

Changed it to ^kt.

 

It might help people to understand the problem if you define the terms in the equation.

Alright

 

A= total annuity

P= principal

R= rate (as a decimal)

k= # of times compounded annually

t= time (in years)

 

Nevermind I figured it out. Turns out I had the wrong formula in the first place...