1. 10-2 Estimating and Finding Area Course 1 Warm Up Warm Up Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day

2. Warm Up 1. What is the perimeter of a square with side lengths of 15 in.? 2. What is the perimeter of a rectangle with length 16 cm and width 11 cm? 60 in. 54 cm Course 1 10-2 Estimating and Finding Area

3. Problem of the Day Two wibbles equal four wabbles, and eight wabbles equal two bibbles. If a square has a perimeter of 16 wibbles, what is its area in square bibbles? 4 square bibbles Course 1 10-2 Estimating and Finding Area

4. Learn to estimate the area of irregular figures and to find the area of rectangles, triangles, and parallelograms. Course 1 10-2 Estimating and Finding Area

5. Vocabulary area Insert Lesson Title Here Course 1 10-2 Estimating and Finding Area

6. The area of a figure is the amount of surface it covers. We measure area in square units. Course 1 10-2 Estimating and Finding Area

7. Additional Example 1: Finding the Area of an Irregular Figure Find the area of the rectangle. Count full squares: 19 red squares. Count almost-full squares: 9 blue squares. Count squares that are about half- full: 4 green squares = 2 full squares. Do not count almost empty yellow squares. Add. 19 + 9 + 2 = 30 The area of the figure is about 30 mi. 2 Course 1 10-2 Estimating and Finding Area

8. Try This: Example 1 Estimate the are of the figure. Count full squares: 11 red squares. Count almost-full squares: 5 green squares. Count squares that are about half- full: 4 blue squares = 2 full squares. Do not count almost empty yellow squares. Add. 11 + 5 + 2 = 18 The area of the figure is about 18 mi. 2 = mi 2 Course 1 10-2 Estimating and Finding Area

9. Course 1 10-2 Estimating and Finding Area

10. Additional Example 2: Estimating the Area of a Rectangle Find the area of the figure. Write the formula. Substitute 15 for l. Substitute 9 for w. A = lw A = 15 9 A = 135 The area is about 135 in 2. 15 in. 9 in. Course 1 10-2 Estimating and Finding Area

11. Try This: Example 2 Find the area of the figure. Write the formula. Substitute 13 for l. Substitute 7 for w. A = lw A = 13 7 A = 91 The area is about 91 in 2. 13 in. 7 in. Course 1 10-2 Estimating and Finding Area

12. You can use the formula for the area of a rectangle to write a formula for the area of a parallelogram. Imagine cutting off the triangle drawn in the parallelogram and sliding it to the right to form a rectangle. The area of a parallelogram = bh. The area of a rectangle = lw. The base of the parallelogram is the length of the rectangle. The height of the parallelogram is the width of the rectangle. Course 1 10-2 Estimating and Finding Area

13. Additional Example 3: Finding the Area of a Parallelogram Find the area of the parallelogram. Write the formula. Multiply. A = bh 2 ft 1 2 A = 2 1 1 2 __ 1 4 Substitute 2 for b and 1 for h. 1 2 __ 1 4 A = 5 2 __ 5 4 A = or 3 25 8 ___ 1 8 __ The area is 3 ft 2. 1 8 __ 1 4 1 ft Course 1 10-2 Estimating and Finding Area

14. Try This: Example 3 Find the area of the parallelogram. Write the formula. Multiply. A = bh A = 1 3 1 2 __ 1 2 Substitute 1 for b and 3 for h. 1 2 __ 1 2 A = 3 2 __ 7 2 A = or 5 21 4 ___ 1 4 __ The area is 5 ft 2. 1 4 __ 1 1 ft 2 1 3 ft 2 Course 1 10-2 Estimating and Finding Area

15. You can make a parallelogram out of two congruent triangles. The area of each triangle is half the area of the parallelogram, so the formula for the area of a triangle is A = bh. 1 2 __ Course 1 10-2 Estimating and Finding Area

16. Additional Example 4: Finding the Area of a Triangle Find the area of the triangle. Write the formula. Substitute 9.6 for b. Substitute 2.9 for h. Multiply. The area is 13.92 cm 2.A = 13.92 A = bh 1 2 __ A = (9.6 2.9) 1 2 __ A = (27.84) 1 2 __ Course 1 10-2 Estimating and Finding Area

17. Try This: Example 4 Find the area of the triangle. Write the formula. Substitute 8.5 for b. Substitute 3.4 for h. Multiply. The area is 14.45 cm 2. 3.4 cm 8.5 cm A = 14.45 A = bh 1 2 __ A = (8.5 3.4) 1 2 __ A = (28.9) 1 2 __ Course 1 10-2 Estimating and Finding Area

18. Lesson Quiz Find the area of each figure. 1. 2. 3. What is the area of a parallelogram with base 16 in. and height 10 in.? 4. What is the area of a triangle with base 10 in. and height 7 in.? Insert Lesson Title Here 4.5 m 9.2 m 41.4 m 2 24 ft 2 160 in 2 35 in 2 Course 1 10-2 Estimating and Finding Area