Pre Algebra Percents

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One Hundred Pieces
Percents

When we write fifty cents as a number,

sometimes we use a decimal point:

$ 0.50

Sometimes we don't use a decimal point.

We write fifty cents like this:

50¢

This "¢" thing is called the CENT sign.

Big news, eh?

Anyway, CENT means one hundred in some language.

The cent sign says that the dollar is chopped up into 100 pieces

and the number next to it is how many we have

(kind of like a fraction ya know).

Math types thought that was kind of neat

and came up with the word PERCENT.

The "per" part means "divided by."

So Percent means:

divided by 100

A percent is a special kind of fraction.

It is soooo special that it gets it's own special squiggle.

They wanted the squiggle to LOOK like a fraction,

but not BE a fraction. They came up with this:

So:

Now we have 3 ways to write fifty out of one hundred pieces of anything.

Examples:

.38	=	38%

.73	=	73%

1.06	=	106%

1.00	=	100%

6.02	=	602%

10.31	=	1031%

See how it works?

Say you want to make a decimal number into a percentage.

Just move the decimal point 2 places to the right

and tack on the "%."

Example:

Change 3.81 to a percent (%).

Step 1:

Step 2:

Example:

Change .153 to a percent:

Step 1:

Step 2:

Since we can change a decimal number to a percent,

it should be no big shock

that we can change a percent back to a decimal number.

Just erase the % sign

and move the decimal point two places to the left.

Example:

Change 32% to a decimal number:

Step 1:

Step 2:

To change a percent to a fraction,

get rid of the "%" and put 100 under the number.

Example:

Change 33% to a fraction:

Step 1:

Step 2:

Example:

Change 3.5% to a fraction:

Step 1:

Step 2:

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