Saturday, January 28, 2023

TI-30 XIIS and Casio fx-115ES Plus 2nd Edition: The Percent Function

TI-30 XIIS and Casio fx-115ES Plus 2nd Edition:  The Percent Function



%:  Divide by 100


Unlike computer languages, where the % symbol usually means modulo division, the % divides the argument by 100 on calculators such as the TI-30 XIIS and Casio fx-115 ES Plus 2nd Edition.


Hence 50% returns 0.5


This may provide confusion when the following is typed:


100 + 50% 


which would returns 100.5 instead of the expected 150.   


Here is how to use the percent function to our advantage in common situations.



Adding and Subtracting Percent


x + p% and x - p%


1.  Enter x and store it in a variable, preferably A.   The variable A can be advantageous, especially the TI-30 XIIS.   Access the variable A on the TI-30 XIIS by pressing [MEMVAR] [ = ] with every few keystrokes.  


2.  Enter the following:


Add percent:  A+A×p%

Subtract percent:  A-A×p%


We can omit the multiplication sign on the TI-30 XIIS.  The multiplication sign is required on the fx-115ES Plus.


Examples:


50 + 10%:   50 → A;  A+A*10%  returns 55


50 - 10%:  50 → A;  A-A*10% returns 45



Percent Change


Key strokes:  (new - old)/old%


Example:


Find the percent change from 425 to 480:


(480-425)/425%   returns 12.94117647



Financial Calculations


For the following calculations, let i=6% and n=4  (i being the periodic interest, n being number of payments).  We can see the percent function in action.



Future Value of a Present Value:  (1+i%)^n   


(1+6%)^4 returns 1.26247696



Future Annuity Value Factor:  ((1+i%)^n-1)/i%


((1+6%)^4-1)/6% returns 4.374616



Present Annuity Value Factor:  (1-(1+i%)^-n)/i%


(1-(1+6%)^-4)/6% returns 3.465105613



Hope this helps, so we can find additional calculations where this percent function can help with calculations with the TI 30 XIIS and Casio fx-115 ES Plus 2nd Edition.  


Eddie 



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