Discover the Difference Between 10% and 30% of 20000

[vtmike]

Hi,

If I am calculating the percentage of a number let's 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

 

[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!

 

[ImAnEngineer]

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

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

 

[symbolipoint]

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

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.

 

[ImAnEngineer]

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.

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

 

[symbolipoint]

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

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.

 

[qntty]

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.

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

\,
\:
\;
\quad
\qquad

 

[Cantab Morgan]

Another way to think about it...

Suppose you go to a store and see an item on sale for 50% off. Then you go to the store the next day and see that it's been reduced 50% more. Even so, the item isn't free!

The store isn't adding the fifty percents. It's multiplying them.