1. Warm Up
Problem of the Day
Lesson Presentation
Lesson Quizzes

2. Warm Up
1. True or false: If the height of a rectangle equals the base of a parallelogram and the base of the rectangle equals the height of the parallelogram, then the rectangle and the parallelogram have the same area.
2. Find the area of a rectangle with a length of 53 in. and a width of 47 in.
True
2,491 in2

3. Which is a better deal, 3 discs for $5.00 or 4 discs for $7.00?
Problem of the Day
Which is a better deal, 3 discs for $5.00 or 4 discs for $7.00?
3/$5.00

4. Learn to find the area of triangles and trapezoids.

5. You can divide any parallelogram into two congruent triangles
You can divide any parallelogram into two congruent triangles. So the area of each triangle is half the area of the parallelogram.

7. Additional Example 1A: Finding the Area of a Triangle
Find the area of the triangle. 1 2
A = bh
Write the formula. 1 2
Substitute 20 for b and 12 for h.
A =
(20 · 12) 1 2
A =
(240)
Multiply.
A = 120
The area is 120 ft2.

8. Reading Math
An altitude of a triangle is a perpendicular segment from one vertex to the line containing the opposite side. The length of the altitude is the height.

9. Additional Example 1B: Finding the Area of a Triangle
Find the area of the triangle. 1 2
A = bh
Write the formula. 1 2
Substitute 30 for b and 24 for h.
A =
(30 · 24) 1 2
A =
(720)
Multiply.
A = 360
The area is 360 in2.

10. Find the area of the triangle.
Check It Out: Example 1A
Find the area of the triangle. 1 2
A = bh
Write the formula. 1 2
Substitute 5 for b and 8 for h.
A =
(5 · 8)
8 in. 1 2
5 in.
A =
(40)
Multiply.
A = 20
The area is 20 in2.

11. Find the area of the triangle.
Check It Out: Example 1B
Find the area of the triangle. 1 2
A = bh
Write the formula.
A = 1 2
(4 • 24)
Substitute 4 for b and 24 for h. 1 2
24 ft 1 2
A =
(108)
Multiply.
4 ft 1 2
A = 54
The area is 54 in2.

12. Additional Example 2: Application
The diagram shows the section of a forest being studied. What is the area of the section? 1 2
A = bh
Write the formula. 1 2
Substitute 43.9 for b. Substitute 16 for h.
A =
(43.9 • 16) 1 2
A =
(702.4)
Multiply.
A = 351.2
The area is km2.

13. Substitute 48 for b. Substitute 24.5 for h. A = (48 · 24.5)
Check It Out: Example 2
The diagram shows the section of a park being studied. What is the area of the section?
24.5 m
48 m 1 2
A = bh
Write the formula. 1 2
Substitute 48 for b. Substitute 24.5 for h.
A =
(48 · 24.5) 1 2
A =
(1176)
Multiply.
A = 588
The area is 588 m2.

15. Additional Example 3: Finding the Area of a Trapezoid
Find the area of the trapezoid. 1 2
A =
h(b1 + b2)‏
Use the formula.
A = 1 2
· 4( )‏
Substitute 4 for h, 14 for b1, and for b2. 1 2
A = 1 2
· 4(26 )‏
A = 53
Multiply.
The area is 53 yd2.

16. Find the area of the trapezoid.
Check It Out: Example 3
12 cm
Find the area of the trapezoid.
7 cm
16 cm 1 2
A =
h(b1 + b2)‏
Use the formula. 1 2
Substitute 7 for h, 16 for b1, and 12 for b2.
A =
· 7( )‏ 1 2
A =
· 7(28)‏
A = 98
Multiply.
The area is 98 cm2.

17. Lesson Quizzes
Standard Lesson Quiz
Lesson Quiz for Student Response Systems