Exercise 1 2 Evaluate xy when x = 7 and y = 8. 28

Exercise ab 2 Evaluate when a = 18 and b = 12. 108

Exercise 1 2 Evaluate (c + d)f when c = 3, d = 4, and f = 10. 35

Exercise r 2 Evaluate (s + t) when r = 7, s = 5, and t = 4. 31.5

A B C D

D A B C

Formula: Area of a Triangle 1 2 A = bh

Altitude An altitude is a segment drawn from any vertex of a triangle perpendicular to the line containing the opposite side.

A C B A C B C A B

C A B

A C B D A C B D A C D B

Example 1 Find the area of ∆XYZ. 324 cm2

Example What is the area of a triangle with b = 12 units and h = 9 units? 54 units2

Example If the base of a triangle is 10 units and its area is 100 units2, what is its height? 20 units

Example If the height of a triangle is equal to its base, what is its height if its area is 72 units2? 12 units

Example What is the area of the triangle below? 27.125 units2 3 4 8 a

Example What is the length of altitude a in the triangle below? 8 7 a 3 4 6.78125 units

b2 h b1

b2 b1 h b1 b2

Formula: Area of a Trapezoid A = (b1 + b2)h The area of a trapezoid (A) is half the sum of the bases (b) times the height (h). 1 2

Example 2 Find the area of the trapezoid. 13 cm 8 cm 18 cm 124 cm2

Example What is the area of a trapezoid with b1 = 8 units, b2 = 11 units, and h = 6 units? 57 units2

Example If the longer base of a trapezoid is twice the shorter base, its height is 8 units, and its area is 48 units2, what is the length of each base? 4 units and 8 units

Example Find the area of the shaded triangle. 12 6 3 9 units2

Example Find the area of the shaded trapezoid. 16 10 5 60 units2