TVM Calculation Error

Things that aren't right, that are in the queue to be fixed... along with workarounds.
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sanman
Posts: 2
Joined: Sat Jul 07, 2012 1:10 pm

TVM Calculation Error

Post by sanman » Sun Jul 08, 2012 8:40 pm

Just got the Calc-12E, ver. 3.4.0.01, and found out is basically useless to do TVM calculations.
For example try
n = 36
PV = -5,000
PMT = -250
FV = 16,000

solving for i gives me 0.533.

The correct answer should be 0.546.

I want my money back!

theDev
Posts: 237
Joined: Mon Aug 04, 2008 8:58 pm

Re: TVM Calculation Error

Post by theDev » Wed Jul 11, 2012 8:16 pm

Hi Sanman (and welcome BTW).

Sorry I didn't get this "right away", this board is pretty quiet. What you're run into is a pretty common point of confusion that we all had when learning the 12C. Namely, that the TVM computations can be made with the payment made at the beginning or end of the period--and when the payment is made (naturally) affects the results.

If you look above the "CHS" key, you'll see 'begin', which means the computations are being made with the payment at the beginning of the period. And the correct answer is i=0.533 for payments-at-the-beginning. I confirmed this on my "real" 12C (g-BEG)...

To switch payments at the end of the period, tap the little 'begin' and it'll change to 'END'.

Rerunning your example with payments at the end of the period does indeed yield i = 0.546 as expected.

What I always found confusing on the "real" 12C was that it only annunciated when set to BEGIN, so you really had to know that "nothing" meant that it was assuming payments at the end. I tried to fix that!

I hope this helps. And if you have other questions, it's way faster to email me at customerservice (capital 2) stonemeadowdevelopment dot com. <-- "spelled out" to keep the robots from spamming the email...

(perhaps you might take pity on an indie developer and adjust your app store review? :| )

Kim

sanman
Posts: 2
Joined: Sat Jul 07, 2012 1:10 pm

Re: TVM Calculation Error

Post by sanman » Wed Jul 11, 2012 9:00 pm

Got it, thanks for clarification. User error!
Will change the rating on app store.

theDev
Posts: 237
Joined: Mon Aug 04, 2008 8:58 pm

Re: TVM Calculation Error

Post by theDev » Thu Jul 12, 2012 5:34 pm

Thanks so much for updating your review--it really does matter what people say.

Kim

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