Tying B.

asked • 09/14/15

What is 0.3 of 80

 
 My math hurts me help 

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Mark M. answered • 09/14/15

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0.3 of 80      "of" usually means multiply
0.3 · 80
24                or
 
(3/10)(80/1)
240/10
24
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David W.

As Mark M. wisely pointed out, 0.3 and 3/10 and 30% are "three tenths."
The problem could have been written as:
  "What is 3/10 of 80?" or  "What is three tenths of 80?"  or
  "What is 30% of 80?" or  "What is thirty percent of 80?"
 
[p.s., When you said your "math hurts," you summed up the situation very nicely.]
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09/14/15

Timothy M. answered • 09/14/15

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Hello,
 
If 0.3 is a proportion, you can find a given proportion of a number by multiplying them together.
In your example, that would be 0.3*80 = 24.
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Mark M.

A proportion is the equality of two ratios.
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09/14/15

Timothy M.

Thanks, Mark.
Another definition for proportion is the fraction of the total that possesses a certain attribute. In statistics, we typically express this as a decimal though
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09/14/15

Mark M.

http://www.mathgoodies.com/glossary/term.asp?term=proportion
 
 
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09/14/15

Mark M.

In mathematics a term can have only one definition. 
A fraction of a total, is just that, a fraction. It is not a proportion.
The conflation may have arisen by the fact that a proportion is expressed as the equality of two ratios (fractions).
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09/14/15

Timothy M.

Thanks for the comment.
It is quite common for a word to have multiple meanings - this is known as a homonym. This is true even in mathematics - especially across disciplines such as statistics and pure mathematics. Statisticians commonly do refer to the fraction of the total that possesses a certain attribute as a proportion. Unfortunately, as much as we might like it to be true, no amount of asserting the opposite will change that.
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09/14/15

Mark M.

As a native speaker of English, I understand the meaning of homonyms, synonyms, and homophones (and I graduated from high school - before Google!). These matters are irrelevant to the discipline of mathematics.
At the present this site deals with questions generally from students in high school mathematics. In that realm, with which I have some familiarity, statistics is either an elective or a subsection of Algebra. In any case the definition of proportion is specific in mathematics.
The number of people holding a position does not determine it's validity.
"Truth does not change according to our ability to stomach it."
~ Flannery O'Connor
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09/14/15

Mark M.

This is not a matter of homonyms, synonyms, homophones, or any other matter of semantics. It is a definition.
The validity of an idea/concept is not determined by the number of people who hold it.
"Truth does not change according to our ability to stomach it."
~ Flannery O'Connor
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09/14/15

Mark M.

"Truth does not change according to our ability to stomach it."
~ Flannery O'Connor
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09/14/15

Timothy M.

Thanks for the comment, but I'm no longer sure what point you wish to make.
If that was meant as a counter-argument, then it seems you have added the appeal-to-authority fallacy to your earlier proof-by-assertion fallacy,
If not, then it seems like you're simply upset by the fact that statisticians use proportion in this way. It is difficult to tell as you do not attempt to dispute the fact that statisticians use proportion in this way.
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09/14/15

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