HP 20B - Manual (Page 29)

Mathematical Calculations
29
To find a percentage of a given number, enter the number and multiply it by the desired percentage, followed by
=
. For
example, to find 25% of 200, press
200*25%=
to return a result of 50 .
To add or subtract a percentage of a number, enter the first number, followed by
+
or
-
and the percentage followed
by
%
. Finish your calculation with
=
. For example, to add 10% to 50, press
50+10%=
to
return a result of 55 .
In RPN mode, the
%
key calculates x % of the number on Level 2 of the stack, when x is the number on Level 1 of the
stack. It does not modify the number on Level 2 of the stack, and thus allows you to perform addition or subtraction after
pressing
%
to add or subtract x % from the number.
For example,
200I25%
returns 50 , but 200 is still on Level 2 of the stack, and pressing
-
returns 150 , or 200-25%.