# Percentage help

1. Apr 13, 2009

### vtmike

Hi,

If I am calculating the percentage of a number lets say 10% of 20000 which is 18000
Then I take 20% of 18000 which is 14400

Why is this not the same as taking 30% of 20000? When I take 30% of 20000 I get 14000. Why is there is a difference of 400?

Thanks,
Mike

2. Apr 13, 2009

### arildno

In order to take away 10% of 20000, we multiply: 0.90*20000=18000.

to take 20% away from 18000, we have: 0.80*18000=0.80*(0.90*20000)=0.72*20000=14400.

Thus, to take away 10% of 20000, and then take away 20% FROM THE REMAINDER, is the same as taking 28% of the ORIGINAL AMOUNT (i.e, 20000)!

This is NOT the same as taking away 30% of the original amount!

3. Apr 14, 2009

### ImAnEngineer

$$0.90 \cdot 0.80 \cdot 20,000 \ne 0.70 \cdot 20 000$$

Because
$$0.90 \cdot 0.80 = 0.72 \ne 0.70$$

4. Apr 14, 2009

### symbolipoint

10% of 20000 means one tenth of 20000. Partly using number characters to express that, you ask for $$\frac{1}{10}$$ of 20000.
That in effect is expressed as $$\frac{1}{10}$$$$\times$$20000

EDIT: I am looking for a way to edit that after it's already published; I know it looks bad. There is no tools button field and I do not have the typeset tags memorized. I want a space between the fraction and the multiplication symbol and I want a space between the multiplication symbol and the 20000.

Last edited: Apr 14, 2009
5. Apr 14, 2009

### ImAnEngineer

You could use \cdot like I did :)
BTW, why don't you just make one Latex code ?

6. Apr 14, 2009

### symbolipoint

My description broke the work into two separate steps; the second one looks bad. The description during the bulk of my post was intended to be descriptive and helpful.

I see what you mean, to put the tex code all in one piece. If I still had my texAid program in use this would be very easy.

7. Apr 14, 2009

### qntty

Here are the commands for extra space in LaTeX, in order from smallest space to largest.

Code (Text):

\,
\:
\;