Lesson objective: Add fractions of unlike denominators using base ten models (flats).

This lesson helps to build procedural skill with adding fractions with denominators or 10 or 100. Base ten flats are used here because it supports the conceptual understanding and growth in regards to place value. This work develops students' understanding that decimal fractions can be written in either fraction or decimal form, and students can use fractions to add decimal values with this conceptual understanding.

Students engage in Mathematical Practice 4 (Model with mathematics) as they use base ten flats to draw conclusions about adding fractions with different denominators (10 and 100 only), and as they write equations to represent a model.

**Key vocabulary:**

- decimal
- denominator
- flat
- model
- numerator
- representation
- rod
- unit
- tenth
- hundredth
- whole

**Special materials needed:**

- base 10 manipulatives
- paper copies of flats
- paper copies of rods
- tiles