Lesson objective: Use the relationship between multiplication and addition to solve real world problems involving area.

Students bring prior knowledge of the concept of area from 3.MD.C.7a. This prior knowledge is extended to using addition and multiplication to solve real world problems involving area as students begin to see the relationship between addition and multiplication when solving for area of a rectangle. A conceptual challenge students may encounter is translating an addition equation into a multiplication equation.

The concept is developed through work with an area model, which can be decomposed into rows of the same number of square units.

This work helps students deepen their understanding of operations because the operations of addition and multiplication are used to solve area-related problems.

Students engage in Mathematical Practice MP8 (look for and express regularity in repeated reasoning) as they discover that the total number of square units in an area model can be determined through either repeated addition or by multiplying the number of columns by the number of rows.

**Key vocabulary:**

- area
- column
- equation
- operation
- row
- square units

**Special materials needed:**