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**atran****Member**- Registered: 2013-07-12
- Posts: 91

Hi,

What's the difference between "value" and "quantity"?

Thanks for help.

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,020

hi atran

I would use 'value' in equations and formula such as

What value of x makes this equation true ... 2x + 3 = 17 ?

If F = 9C/5 + 32 ... what is the value of F if the value of C = 40 ?

I would use 'quantity' when measuring something such as

What quantity of sand is needed to make a 3:1 concrete mix if I have 25 kilos of cement.

I think you can always change 'what quantity of' to 'how much'; thus

How much sand is needed .......................?

EDIT: I've just looked on dictionary.com and found this:

value 6. maths

a. a particular magnitude, number, or amount: the value of the variable was 7

b. the particular quantity that is the result of applying a function or operation for some given argument: the value of the function for x=3 was 9

Interesting that they use the word quantity whilst defining value.

quantity

4. Mathematics .

a.

the property of magnitude involving comparability with other magnitudes.b.

something having magnitude, or size, extent, amount, or the like.c.

magnitude, size, volume, area, or length.

So perhaps the main difference is that value is used when you want to be specific, such as

I have a number of piles of objects. I know the quantity of objects in each pile. Which value will satisfy this specific requirement ..............

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**atran****Member**- Registered: 2013-07-12
- Posts: 91

Thank you Bob.

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**atran****Member**- Registered: 2013-07-12
- Posts: 91

Is it right to think this way: quantity is amount, and a value is a computed or assigned quantity/number.

What is a number then? What's the difference between quantity and number?

*Last edited by atran (2013-09-21 03:35:58)*

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**atran****Member**- Registered: 2013-07-12
- Posts: 91

Using my thesaurus,**value**: "a numerical quantity measured or assigned or computed"**quantity**: "how much there is or how many there are of something that you can quantify"**number**: "the property possessed by a sum or total or indefinite quantity of units or individuals"

I don't really understand the definition of a number: Is it safe to say that it's an abstract quantity?

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 95,993

Hi;

Ricky once proved that lots of definitions in dictionaries eventually were circular. It led me to distrust them, especially when dealing with math definitions.

Wiki wrote:

A number is a mathematical object used to count, label, and measure.

**In mathematics, you don't understand things. You just get used to them.**

**If it ain't broke, fix it until it is.**

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**knightstar****Member**- Registered: 2014-03-12
- Posts: 14

**MATHEMATICS****Mathematics** is the science of quantities

Number is the symbol for a known quantity

Variable is the symbol for an unknown quantity

Amount is the extent of something

Value is a known numerical amount

Quantity is a known or unknown numerical amount

In other words, a quantity is always a value, but a value is not necessarily a quantity. Take for example the variable, which is a quantity that can have different values.

*Last edited by knightstar (2014-03-20 08:01:31)*

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