calculate monthly payments (TVM_PMT)

[Dennis Malen]

Perhaps I misundstand how this formula is to be used. I created a program in 
filepro that calculated the monthly payment on a mortgage. We have used it 
for years. My answer comes in at $89.74. I asked someone else to verify on a 
calculator. They came up with the same answer.

I am also providing a copy of the original email which also indicated they 
got $89.74.

If this formula is not to be used for calculating a monthly payment then 
obviously it will be wrong. I thought I could save many lines of programming 
the long way in filePro as opposed to the simplicity and ease of use of this 
formula.

In any event, here is the old post and resolution:

STARTS HERE:

Believe it or not at 4/12/2009 11:20 PM, Kenneth Brody said:
>Robert T. Repko (R Squared Consultants) wrote:
>>Believe it or not at 4/12/2009 10:46 PM, Kenneth Brody said:
>>>Robert T. Repko (R Squared Consultants) wrote:
>>>>Does anyone have a routine that calculates monthly payments based on an 
>>>>APR.
>>>Would the TVM_PMT() function do what you're looking for?
>>I looked at that function but it gives me a different answer than the 
>>calculators I've used for finding payments based on an APR.  Before I 
>>started working on the program I used calculators on the Internet so I 
>>would know what answers I was supposed to get.  I used $1000.00, 13.9%, 
>>for 12 months, compounded monthly.  Using TVM_PMT() I get a monthly 
>>payment of 84.09, with a calculator I get 89.74.  The description doesn't 
>>mention if it's simple or compound interest.
>
>Hmm...
>
>     xx(8,.2) = tvm_pmt("12","13.9"/"12","1000","0")
>
>gives me "-89.74", just like your calculator.
>
>What did you do that gave you a different number?
>
>--
>Kenneth Brody

I followed the example Laura had in her help file.
Interpreting the numbers in her example $200,000, 360 months (30 yr
loan), at 7.25%

      if: ' What would be the payment for this loan?
    then: PMT = TVM_PMT("360",".0725","200000","0") ' PMT will 
be -631.40595650

I used:
eh=TVM_PMT("12",".139","1000","0")

I see my mistake, instead of using a monthly rate (.139/12) I used
the APR of .139 in the calculations.

Thanks Ken I never would have seen my error.  I hate when I do that,
spend days on a problem and the solution is right under my nose and I
can't see it.

END OF OLD EMAIL

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Dennis Malen
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----- Original Message ----- 
From: "Kenneth Brody" <kenbrody at spamcop.net>
To: "Dennis Malen" <dmalen at malen.com>
Cc: <filepro-list at lists.celestial.com>
Sent: Thursday, October 22, 2009 1:19 PM
Subject: Re: calculate monthly payments (TVM_PMT)


> Dennis Malen wrote:
>> This is from an old post.
>>
>> I used Ken Brody's example in an April 13, 2009 post:
>>
>> tc(10,.2)=TVM_PMT("12",".139"/"12","1000","0")
>>
>> The answer should be -89.74. I get -83.40.
>
> Why do you feel the answer should be "-89.74"?  My HP-12C gives the same 
> answer as filePro -- "-83.40".
>
>> I am on filePro 5.0.14D4.
>>
>> Has this been fixed since then.
>
> I see nothing that is broken.
>
> -- 
> Kenneth Brody