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More Than 100%
Name: Robert
Status: student
Age: N/A
Location: N/A
Country: N/A
Date: N/A
Question:
I am trying to understand percentages. I
understand that it is a formula such as the part/whole x 100
gives me a percent answer, but if 100% is the whole value, how
can I get 300%? Is this considered the percent change from the
original value or would it be better explained as three times the
original value?
Replies:
You raise an important issue that is flagrant in both scientific
and non-scientific literature. It is absolutely necessary when
expressing percentages, to specify the percentage of WHAT!!
Example: If a salt doubles its solubility if the temperature is
raised from 25C to 50C it is OK to say the solubility increases by
200% = 2 x 100/%, but without specifying that the basis of the
percentage is the solubility at 25C., the 200% has no meaning.
Unfortunately, in socially charged issues protagonists and
antagonists often toss out percentages without specifying the basis
of the percentage.
An intentionally skewed example: "The population of the US has
increased by 1000%." But what is the present population compared to
-- the last census, or the estimated population in 1800?
I refer you to the classic book "How to Lie with Statistics" by
Darrell Huff for more subtle examples of the misuse of numbers.
Vince Calder
Robert,
100% means the whole value of reference. You cannot just have 100%. You
must have 100% of something, or more often 100% of an amount. Less than
100% is less than that amount. More than 100% is more than that amount.
300% of $15.00 is (300/100)*($15.00)=$45.00. You cannot receive 300% of the
$15.00 from the wallet that holds that original $15.00, but you can get it
from a different source. You can get it from a bet at the racetrack. Odds
of 3-to-1 mean that if you win, you will get 300% of the original bet as
winnings. Of course, you will also get back your original bet money.
Dr. Ken Mellendorf
Physics Instructor
Illinois Central College
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Update: June 2012
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