Percentage problems :S:S HELP

[Bouncing]

Right, I understand on a caluclator to find 20% of like 150 it would be 150 x 20 then divide by 100.

But what I don't understand is when I'm not using a calculator I would just do find 10 percent of 150 which is 15 (divide by 10) and then times 15 x 2 which is thirty? So there both thirty percent which is confusing. But heres the question I was doing which confused me with both equations.

In 2006 population of a town was 68 000
By 2007 the population had decreased by 3.2%

Work out the population of the town in 2007.
So I know the final answer now is 65824, but if the .2 equals 20 percent surely you would do 10% which is 6800 then x 2 which is 136 00
Then on the calculator it says to do for 20 percent 68 000 x 20 / 100 which is 136 00 too but then 30% is 68 uch im so confused then id add the 30% and 20% somebody just help me because apparantly 2176 is 3.2% :S:S:S

[ben]

I dont understand what you mean whats actaully wrong? lol

[LoveToStack]

just help me because apparantly 2176 is 3.2% :S:S:S

I also don't really understand what the problem is but 3.2% would be 2176. The way I always do it is; 1%= 0.01x w/e the number is. So 3.2%= 0.032x number.
Knowing that you can miss out a step if you do 1-0.032 in your head, you can get your answer if you do 0.968x number then it does it all in one go. The answer being 2176.
Most of the time they just teach you to do original number, call it X for time saving, divided by 100 to get 1% then multiply it by w/e % you're looking to deduct or add on, in this case 3.2%. So if we do it that way we get 1% = 680, so 3.2x680= 2176.

EDIT; after looking over your post and seeing this;

"but if the .2 equals 20 percent"

Just to clarify, the .2 in 3.2 is not 20%, its 0.02% of the whole number. I think you're getting confused with; "0.2 x Number = 20% of original number"

[Bouncing]

Basicially, ill give you another example.

When I do 15% of something lets say 8 I do

10% = 0.8
5% = 0.4

So 15% = 0.12

but when i check it, it says its 1.2 but its on the non-calc part so i cant use a calc so what am i doing wrong

[Lost]

Wait, this isn't really clear... what is actually the problem???

[Bouncing]

Wait, this isn't really clear... what is actually the problem???

Read my new example its clearer

[brandon]

0.8 + 0.4 = 1.20

Think of it like 0.80 + 0.40 = 1.20

0.08 + 0.04 = 0.12

[Bouncing]

why am i such an idiot. I just did a lil mistake *** :@ thanks though brandon

Now does anyone know how to get 3.2% of 68 000 with a calc and without?

[ben]

yeah 1 percent will be 68000/100 I think so thats 680
0.1% you would have to divide by 1000? maybe so 0.1% would be 68

680 x 3 = 2040 (you could work that out on paper)
68 x 2 = 136

so 2040 + 136 = 2176

10% = divide by 10
1% = divide by 100
0.1% = divide by 1000

[Bouncing]

yeah that must be right cheeers

[scottish]

what if i understand;

You want to find 3.2 you do 0.032 x 68000 = 2,176 or
100% - 3.2% = 96.8% = 0.968

so 0.968 x 68000 = 65,824 people left
?

[Bouncing]

Nah that's wrong I rang my tutor hahaha

[scottish]

Whats wrong? lol

[Bouncing]

Oh sorry mate, the first bit is right when you got 2176 and you take that, but 0.968 don't really see how you can get two different answers?

[scottish]

IF they ask you; the population for '06 is 68000, in '07 it decreases by 3.2% how many people are left

then you'd use the 0.968 as its finding 96.8% of the population (which is 100% - 3.2%; you could also do 68000-2176 to get same answer)

but if they asked you it decreased by 3.2%; how many people is that then tis the 0.032 x 68000 which is 2176 :P

[Bouncing]

haha yeah thanks nice to know you help