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I have a loan for a principal amount of \$117,000.00 at 9.75% interest and a total amount due (including the interest for 84 months) of \$191,805.60. I had 84 months to pay it off, or I could pay it off early, without penalties. I have made 61 payments totalling \$139,287.40.

How do I calculate the principal balance due, not including any further interest?

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    this question is not fit for asking here.2012-03-30
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    @TaoHong洪涛 Why not? How would you solve such a problem? I would use math.2012-03-30
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    I'm a bit confused. Is the 9.75% a monthly or annual interest? compound of course, right?2012-03-30
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    @TaoHong洪涛: why not? seems like a legitimate mathematical question to me. The [faq] explicitly says: *Mathematics - Stack Exchange is for people studying mathematics at any level [...]*2012-03-30
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    The interest is compound, but there is an early payoff clause, that I don't need to pay interest on the principal balance that is left and that I now want to pay off.2012-03-30
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    Just in case I did not answer your question, I borrowed $117,000.00 at 9.75% for 84 months, which comes to a total amount due,(if I take the full 84 months to pay it off) of $191,805.60. However, I want to now pay off the balance (principal balance left, without interest). Is that enough info?2012-03-30
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    @t.b. maybe should be asked here http://money.stackexchange.com/2012-03-30
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    This is financial mathematics. I am teaching a class where we do problems like this.2012-03-30
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    @Mindy: There are a few things one needs to know. The most important is whether the $9.75$ is the *nominal* yearly rate, or the *effective* annual rate. If nominal, then interest rate is likely $9.75/12$ monthly, compounded monthly, which means effective annual rate is higher than $9.75$. One will also have to know whether the $61$ payments were all equal.2012-03-30
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    @Graphth then we're expecting you to post an answer :)2012-03-30
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    @J.D. I assume the answer to Andre's last question is the payments are all equal, but I don't know the answer to the first question. Is it a nominal annual rate, or an annual effective rate? I can't answer it without knowing that.2012-03-30
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    @Mindy Do you have any updated on the inconsistency I mentioned in my answer below?2012-04-03

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