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# Number Relations: GED Test Prep (page 6)

By LearningExpress Editors
LearningExpress, LLC
Updated on Mar 9, 2011

### Fractions

To do well when working with fractions, it is necessary to understand some basic concepts. Here are some math rules for fractions using variables:

### Multiplying Fractions

Multiplying fractions is one of the easiest operations to perform. To multiply fractions, simply multiply the numerators and the denominators, writing each product in the respective place over or under the fraction bar.

### Dividing Fractions

Dividing fractions is the same thing as multiplying fractions by their reciprocals. To find the reciprocal of any number, switch its numerator and denominator.

For example, the reciprocals of the following numbers are:

When dividing fractions, simply multiply the dividend by the divisor's reciprocal to get the answer.

### Adding and Subtracting Fractions

To add or subtract fractions with like denominators, just add or subtract the numerators and leave the denominator as it is.

To add or subtract fractions with unlike denominators, you must find the least common denominator, or LCD.

For example, for the denominators 8 and 12, the LCD is 24 because 8 × 3 = 24, and 12 × 2 = 24. In other words, the LCD is the smallest number divisible by each of the denominators.

Once you know the LCD, convert each fraction to its new form by multiplying both the numerator and denominator by the necessary number to get the LCD, and then add or subtract the new numerators.

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