## Lesson: Adding and Subtracting Fractions With Like Denominators

Developing the Concept

When we teach students to add and subtract, we encourage them to work from right to left. For whole numbers, this means starting in the ones place and then working with the tens, then the hundreds, and so forth. To reinforce this habit, encourage students to compute with the fraction parts of mixed numbers before the whole-number parts. While this is not essential to producing a correct answer in addition, it is important in some subtraction problems, so developing the habit of always working right to left may help students to avoid errors.

**Materials:** rulers marked in half-, fourth-, and eighth-inches; pencils; erasers

**Preparation:** none

**Wrap-Up and Assessment Hints**

When students are comfortable using their rulers to generate the numbers for addition and subtraction problems, pose some problems that involve the denominators 2, 4, and 8. Allow them to refer to their rulers if they need to. When they find these denominators easy, pose problems with denominators of 3, 6, and 10.