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Finding Percentages on a Calculator

Date: 06/22/2006 at 20:15:50
From: Donna
Subject: How do I use a calculator to check percentages

How do I use a calculator to check percentages?  For example, how 
would I check 6% of 180,000 using a calculator?  Would I multiply
180,000 x 6.00%?



Date: 06/22/2006 at 22:55:39
From: Doctor Peterson
Subject: Re: How do I use a calculator to check percentages

Hi, Donna.

Probably!

Unfortunately, I've seen some variation in how calculators handle
percents, so you'll want to check the instructions that came with 
yours to be sure.  But try it out and see!  What I'd do, if I had an
unknown calculator with a % key, is to enter something like

  200 x 5 % =

and see if it gave the right answer, namely 10.  (Also note whether it
gives the answer even before you press "="; some work that way, and
then you should learn NOT to use "=" here.  That is true, for example,
of the calculator that comes in Windows.)

Then I might also try

  5 % x 200 =

and see if that worked too.  (On many calculators, it won't, so I'd
have learned not to do it in that order!)

There's much more variation in how they handle percentage increases, like

  200 + 5 %

which many calculators, but not all, would take as "increase 200 by
5%", giving 210.  If you need to do things like that, you'll want to
be sure to check the manual.

If you have any further questions, feel free to write back.


- Doctor Peterson, The Math Forum
  http://mathforum.org/dr.math/ 
Associated Topics:
High School Calculators, Computers
Middle School Fractions

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