The Rule: When adding fractions that have the same bottom number (denominator), you only add the top numbers (numerators). The bottom number stays exactly the same.
Example 1: Pizza
If I eat 2/8 of a pizza, and my brother eats 3/8 of the same pizza, we just add the tops. 2 + 3 = 5. So we ate 5/8 of the pizza together. We don't add 8+8 because there are still only 8 slices in the whole pizza.
Example 2: Distance walked
I walked 1/4 of a mile to the park, and then another 2/4 of a mile to the store. 1/4 + 2/4 = 3/4. I walked 3/4 of a mile in total.
Teacher Annotation: Great pizza example!
Example 3: Time
I played games for 2/6 of an hour, and then read for 1/6 of an hour. 2/6 + 1/6 = 3/6. This is the same as half an hour!