1. Fractions and Decimals
Lesson 20
Fractions and Decimals
Area with Fractions

2. Warm-Up

3. Area with Fractions Target:
Calculate areas of rectangles, squares and triangles with lengths of sides that are fractions or mixed numbers.

4. Vocabulary Area: The number of square units used to cover a surface.
Perpendicular: Two lines or segments that form a right angle.

5. Formulas

6. Example 1 Find the area of the rectangle.
Formula: Area = length × width.
Change to improper fractions.
Multiply.
Simplify.
The area of the rectangle is 10 units2.

7. Example 2 Find the area of the square. Formula: Area = side × side.
Change to improper fractions.
Multiply.
Simplify.
The area of the square is feet2.

9. Formulas

10. Example 3 Find the area of the triangle.
Formula: Area = × base × height
Change whole numbers to
improper fractions.
Multiply.
Simplify.
The area of the triangle is inches2.

11. Exit Problems
Find the area of a rectangle that has a length of units and a width of units.
Find the area of a square with a side that measures inches.
Find the area of a triangle with a height of inches and a base of inches.
A painter plans to paint a wall that is feet tall and 12 feet wide. What is the area of the wall he will paint?

12. Communication Prompt
Think of a rectangular, square or triangular object in your home. How would you find the area of this object?