# Math Skills Overview Guide

## What does it mean?

### Definitions:

$$\frac{a}{b}$$ where a is called the numerator and b is called the denominator.

Addition $${\frac{a}{b} + \frac{c}{d}} = {\frac{ad + bc}{bd}}$$ Subtraction $${\frac{a}{b} - \frac{c}{d}} = {\frac{ad - bc}{bd}}$$

## What does it look like?

A general example to help you recognize patterns and spot the information you're looking for

Addition Examples: $${\frac{1}{4} + \frac{1}{4}} = {\frac{1 + 1}{4}} = {\frac{2}{4}} = {\frac{1}{2}}$$ $${\frac{5}{7} + \frac{1}{4}} = {\frac{20 + 7}{28}} = {\frac{27}{28}}$$ Subtraction Examples: $${\frac{2}{4} - \frac{1}{4}} = {\frac{2 - 1}{4}} = {\frac{1}{4}}$$ $${\frac{5}{7} - \frac{1}{4}} = {\frac{20 - 7}{28}} = {\frac{13}{28}}$$

## You'll use it...

You use every day dividing items, money and in measuring materials.

## Video

### Finding Common Denominators

Watch a Khan Academy Video »
Length: 4:42

## Video

### Adding Fractions with Like Denominators

Watch a Khan Academy Video »
Length: 3:18

## Video

### Adding Fractions with Unlike Denominators

Watch a Khan Academy Video »
Length: 4:06