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#1 procode200

procode200

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Posted 16 January 2020 - 09:28 PM

With either CASIO fx-CG50 or CASIO fx-991EX

 

Suppose I have a number 13.8888888

Is there one button I can press that would round that to 14?

how about to other solutions like the 10's and the 100's etc.



#2 MJim

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Posted 16 January 2020 - 11:21 PM

Looks like you can do it on both calculators, though with the fx-CG50 the function is buried in menus (OPTNF6F4F4 - the Rnd function), while with the fx-991EX it is just Shift0.

 

If you just want to change the displayed number to show rounded values, you can use the built in number modes to specify the digits:

Fix - Specify the number of decimal points, 0 = no decimal points, 1 = 1 decimal point, etc (fx-CG50 - ShiftMENUF1, fx-991EX - ShiftMENU31)

Sci - Specify the number of significant figures, 1 = 1 significant figure, 2 = 2 significant figures, etc (fx-CG50 - ShiftMENUF2, fx-991EX - ShiftMENU32)

 

These are display modes so it is important to realize that even though the number displayed is changed, the internal precision is maintained.  But either of these modes will display the correctly rounded value for their setting. 

 

Fix 0 (no decimal places)

13.8888888

14.

 

Fix 2 (2 decimal places)

13.8888888

13.89

 

Sci 1 (1 significant figure)

13.8888888

1 x 101

 

Sci 2 (2 significant figures)

13.8888888

1.4 x 101

 

Internally however, they maintain their precision; just because 13.8888888 is shown as 14. does not mean you are calculating with a rounded value, eg let us say you use Fix 0:

13.8888888

14.

Ans+0.6

14.

 

This is because 13.8888888 + 0.6 = 14.4888888, so it's displayed value is rounded down to 14.

 

So this is where the Rnd function comes in; to have the number internally rounded to what is shown on the display.  Once again with Fix 0:

13.8888888

14.

Rnd(         <-- You don't need to type in Ans here as by default it will fill it with Ans automatically after pressing EXE or [=].

14.

Ans+0.6

15.

 

Here 14 + 0.6 = 14.6 which the display will round to 15.  Note that Rnd( doesn't really do any rounding, it just pretty much takes the displayed value and overwrites the internal value with it.  If you type Rnd(13.8888888 it will return 13.8888888.

 

EDIT:

Check out section 2.1 & 2.2 (start of chapter 2) of the fx-CG50 Software manual for some more example usage.  You will notice that there is actually another function called RndFix( that will allow you to round decimal places without changing number modes.


Edited by MJim, 16 January 2020 - 11:37 PM.

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