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Calculate manually with RPN calculator
10-31-2019, 05:13 AM (This post was last modified: 10-31-2019 06:29 AM by Gamo.)
Post: #8
RE: Calculate manually with RPN calculator
Manually calculate the Interest Rate for an Annuity.

Formula use to solve for [ i ] the interest rate when these three variables are known.

n - Period
PV - Present Value
PMT - Payment

f(i) = (PMT ÷ PV) + [ i ÷ 1 - (1+i)^n ]

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Steps: FIX 4

Setup: n [STO] 0 PMT [ENTER] PV [÷] [ENTER] [ENTER] [ENTER] [.] 1

Iterations: [ENTER] [ENTER] 1 [+] [RCL] 0 [Y^X] 1 [-] [÷] [-]

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Example: n = 25, PV = 2000, PMT = 203.61, i = ?

Using HP-12C result is 8.9998 or i = 9%

On the original HP-12C when calculate step to [Y^X] the screen will turn blank momentary.
and resume normal operation.

Calculate Manually:

25 [STO] 0 203.61 [ENTER] 2000 [÷] display 0.1018 [ENTER] [ENTER] [ENTER] . 1

[ENTER] [ENTER] 1 [+] [RCL] 0 [Y^X] 1 [-] [÷] [-] display 0.0916

[ENTER] [ENTER] 1 [+] [RCL] 0 [Y^X] 1 [-] [÷] [-] display 0.0903

[ENTER] [ENTER] 1 [+] [RCL] 0 [Y^X] 1 [-] [÷] [-] display 0.0900

[ENTER] [ENTER] 1 [+] [RCL] 0 [Y^X] 1 [-] [÷] [-] display 0.0900

Last two iterations got the same value based on 4 decimal places.

[EEX] 2 [x] display 9

Answer: 9%

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Note: The [.] 1 is a guess
Hint: For higher decimal place accuracy simply do more iterations.
———————————————————————————

Gamo
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RE: Calculate manually with RPN calculator - Gamo - 10-31-2019 05:13 AM



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