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# Number Relations: GED Test Prep (page 5)

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Updated on Mar 9, 2011

### Subtracting

When subtracting integers, change all subtraction to addition and change the sign of the number being subtracted to its opposite. Then, follow the rules for addition.

Examples

(+10) – (+12) = (+10) + (–12) = –2

(–5) – (–7) = (–5) + (+7) = +2

### Decimals

The most important thing to remember about decimals is that the first place value to the right begins with tenths. The place values are as follows:

In expanded form, this number can also be expressed as:

1,268.3457 = (1 × 1,000) + (2 × 100) + (6 × 10) + (8 × 1) + (3 × .1) + (4 × .01) + (5 × .001) + (7 × .0001)

### Comparing Decimals

Comparing decimals is actually quite simple. Just line up the decimal points and fill in any zeros needed to have an equal number of digits.

Example

Compare .5 and .005

Line up decimal points      .500

Then, ignore the decimal point and ask, which is bigger: 500 or 5?

500 is definitely bigger than 5,

so .5 is larger than .005.

### Variables

In a mathematical sentence, a variable is a letter that represents a number. Consider this sentence: x + 4 = 10. It's easy to figure out that x represents 6.However, problems with variables on the GED will become much more complex than that, so you must learn the rules and procedures. Before you learn to solve equations with variables, you need to learn how they operate in formulas. The next section on fractions will give you some examples.