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```Place Value

Place Value-  A value given to the place a digit is in.

Ten Thousands    	|   4
Thousands           |   6
Hundreds            |    9
Tens                    |    6
Ones                   |     7

Example: Give the place value of the bold number       47, 298

Decimal PLace Value- The shaded area is 2/10.  It can also be 		written is .2.

Tenths                  |        .1
Hundredths          |      .02
Thousandths        |    .003
Ten Thousandths  | .0004

Example:  give the place value of the bold number   4.7862

When you add and subtract decimals, you must line up the decimal places.

Say you have    6.875
+    1.2

To do this, you line up the decimals.  You end up with    6.785
+ 1.2
After you do that, you add/subtract as usual.                 7.985
Mulitiplying Decimals

When you multiply decimals, you do not have to line up the decimals as you would when adding/subtracting decimals.  What you do is multiply the numbers as you normally would.  You then add up the number of decimal places in both numbers and move the decimal point that many places over.

Example:  3.26
*  1.2
652
3260
3.912	There are 3 decimal places, so you move the decimal point 				over 3 spaces.  Your final answer will be 3.912

Dividing Decimals

Dividing decimals is just the same as dividing regular decimals (almost).  When we explain this, it is going to seem a lot harder than it really is.  When dividing decimals and the number inside the braquet has a decimal, you put the decimal point directly above it.

Example:

You then divide as normal.

When the number outside the sign is a decimal, you move the decimal point on the outside number to the right until the number is not a decimal.  With the number on the inside, you move the decimal point to the right as many times as in the outside number.

You then divide as you normally do.

This number keeps going on and on, but not all do.
This is the end of our section on algebra in the World Wide Math Tutor.

Ratios

A ratio is used to compare two quanities.
....
The ratio of the shaded circles is 3 to 4.  You write this ratio as a fraction 3/4.

In 8, 7, 2, 4, and 9, the ratio of odd numbers is 2/3.

Sometimes you will encounter a problem that you have to solve such as:  Two out of every three students like hot dogs opposed to hamburgers.  If there are 24 students in the class, how many like hot dogs better?

In order to solve this problem, you have to make an equation so that the ratios equal each other.

1. 2/3= x/24   In order to find x, find out what times 3 will get 24.  It is 8.

2. 2/3= 16/24 after you multiply by 8.

So 16 out of the 244 kids like hot dogs.

Percents and Ratios

Percent means per one hundred.  We use percents when comparing an number with 100.

Example: If there are 43 dots that are circled and 100 dots total, the ratio is 43 to 100 and it is 43% of 100.

Percents and Decimals

Percents can be interpreted as decimals.  This works in this way: of you have, for example, .23, it is read as 23 hundredths.  23% is equal to that because a percent is per one hundred.  An easier way to turn decimals into percents is by moving the decimal place two timesa to the right.

Example: .43= 43%  .013= 1.3%

To turn a percent into a decimal, you just move the decimal of the percent two times to the left..

Example: 43%= .43  15%= .15   4%= .04

Percents as Fractions

To write a percent as a fraction, all you have to think is that percent means per one hundred.  If you had 25% it would equal 25/1010.  Since 25/100 is not in lowest terms, you reduce it to 1/4.  So 25% equals 1/4.
Other examples are:
50%= 50/100= 1/2		43%= 43/100
55= 5/100= 1/20			80%= 80/100= 4/5

Fractions As Percents

To turn a fraction into a percent, all you have to do is find an equivalent fraction with 100 as the denominator.

For example:  3/4= 75/100= 75%
3/25= 12/100= 12%
Finding a Percent of a Number

If you want to findwhat 20% of 145 is you have to turn the percent into a decimal and then mulitply that by the whole number.
Example:   145
*  .2        20% of 145 is 29
29.00

Beginning Geometry

Geometry is the study of lines, rays, segments, shapes, symmetry, etc.  In this section ofthe World Wide Math Tutor, we will go into basic geometry concepts for elementary school students.  So, if you high school students need some extra info, SORRY!

The first three concepts of geometry are lines, points and segments.

Point- a specific plane on a number line, coordinate graph, or map.
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