1. Cell phone use is prohibited.
Students:
Today is a red light day.
Cell phone use is prohibited.
This is your warning.

2. Area Formula of a triangle: A = ½ • b • h
Find the area of each triangle. 1) 2)
3 in
7 m
10 in
8 m
A = ½ • (10 in) • (3 in)
A = ½ • (8 m) • (7 m)
A = ½ • (30 in2)
A = ½ • (56 m2)
A = 15 in2
A = 28 m2
3) b = 4 yd , h = 9 yd
4) b = 5 ft , h = 8 ft
A = ½ • (4 yd) • (9 yd)
A = ½ • (5 ft) • (8 ft)
A = ½ • (36 yd2)
A = ½ • (40 ft2)
A = 18 yd2
A = 20 ft2

3. 17.04 Area of a Trapezoid

4. Every trapezoid has two bases.
Base 1 ( b1 )
Height (h)
Base 2 ( b2 )
Every trapezoid has two bases.
The height is perpendicular to the two bases.
Area Formula of a Trapezoid
A = ½ • h • (b1 + b2)

5. Area Formula of a Trapezoid
A = ½ • h • (b1 + b2)
Find the area.
4 in
5 m
6 in
3 m
13 m
10 in
A = ½ • (6) • (4 + 10)
A = ½ • (5) • (3 + 13)
A = ½ • (6) • (14)
A = ½ • (5) • (16)
A = ½ • (84)
A = ½ • (80)
A = 42 in2
A = 40 m2

6. Area Formula of a Trapezoid
A = ½ • h • (b1 + b2)
Find the area
h = 7 , b1 = 10 , b2 = 4
h = 8 , b1 = 14 , b2 = 6
A = ½ • (7) • (10 + 4)
A = ½ • (8) • (14 + 6)
A = ½ • (7) • (14)
A = ½ • (8) • (20)
A = ½ • (98)
A = ½ • (160)
A = 49
A = 80

7. Area Formula of a Trapezoid
A = ½ • h • (b1 + b2)
Find the missing part.
b1 = 5 m , b2 = 3 m , A = 32 m2
32 m2 = ½ • (h) • (5 m + 3 m)
32 m2 = ½ • (h) • (8 m)
32 m2 = (h) • (4 m)
8 m = h

8. Area Formula of a Trapezoid
A = ½ • h • (b1 + b2)
Find the missing part.
b1 = 17 ft , h = 7 ft , A = 70 ft2
70 ft2 = ½ • (7 ft) • (17 ft + b2)
140 ft2 = (7 ft) • (17 ft + b2)
20 ft = 17 ft + b2
3 ft = b2