16
Notes on Percentages
A percentage must always relate to a frac-
tional part of something. A statement like
“25%” is meaningless unless it is known
what the whole is. 25% of 40 is 10. 25% of
1,000 is 250, etc.
In the MathMaster, the percent key operates
in two ways, depending upon whether its
use follows an add or subtract operation, or
a multiply or divide operation. It is important
to understand this distinction when using
this calculator (or any other calculator,
for that matter, since different calculators
process percentages in different ways).
In add-on and discount problems, the calcu-
lator always assumes the first number
entered as the whole, of which it finds the
requested percentage. It then displays that
fractional part and uses it as the second
number which is then either added to or
subtracted from the first number (depending
on whether it follows an add or subtract
operation) when the equals key is pressed.
When % is used following a multiply or
divide operation, the MathMaster assumes
the whole to be 1; therefore pressing 16%
