## Lesson: Adding and Subtracting Fractions With Like Denominators

Introducing the Concept

Adding and subtracting fractions with like denominators is just like adding and subtracting whole numbers with the same units. When you add **6 minutes** to **5 minutes**, the sum is **11 minutes**. When you add **6 eighths** to **5 eighths**, the sum is **11 eighths**. Monitor students' understanding of this process—if they don't keep the idea of denominator-as-units in mind, they may continue to ignore the denominator when adding and subtracting fractions with unlike denominators. The sum of 6 hours plus 5 minutes is NOT 11 hours or 11 minutes just as the sum of 6 tenths plus 5 eighths is NOT 11 tenths or 11 eighths.

**Materials:** board or overhead projector

**Preparation:** none

**Prerequisite Skills and Concepts:** Students should be able to add and subtract whole numbers. They should also understand the functions of the parts of a fraction and be able to write fractions in simplest form.