Math CentralQuandaries & Queries


Question from Kenneth:


I saw this definition online from the Free Dictionary (The Free regarding the definition of percent (%):

"Noun 1. a percent sign - a sign (`%') used to indicate that the number preceding it should be understood as a proportion multiplied by 100."

What is this "proportion" multiplied by 100?

When I think of a proportion, I think of a/b = c/d. How can a number preceding the percent sign be understood as a proportion X 100?

I thank you for your reply!

This FREE DICTIONARY definition is a good example of getting what you pay for. It is correct, except that the word “proportion” is used in several ways, one of which is what you correctly recall from your math class. “Proportion” is also used to mean “size, degree, or extent relative to a standard” (according to my WEBSTER’S NEW WORLD COLLEGE DICTIONARY, 3re ed. of 1997). So one might say that the proportion of women at the school is 570 out of 1000. The free dictionary perhaps should have used another word such as ratio, or quotient, or fraction instead of proportion: “…used to indicate that the number preceding it should be understood as a fraction, written in decimal form, multiplied by 100." So, for example,

570/1000 = .57 would represent 57% of the total population.



"Percent'' means "out of a hundred'' or "per hundred'': The "cent'' means hundred, just as in "centimeter'',
which is a hundredth of a meter, or "centipede'' which (figuratively) has a hundred legs or "pedes''.

So 7% means "seven out of a hundred'', the ratio 7/100 which is 0.07. You need to multiply this proportion by 100 to get the 7 in "seven percent''.


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