Area of Triangles

A = 40 cm² The area of this rectangle is 40 cm². If you divide this rectangle in half, what two shapes do you see? A = 40 cm²

A = 40 cm² A = 20 cm² The area of this rectangle is 40 cm². If you divide this rectangle in half, what two shapes do you see? Triangles So if the rectangle’s area is 40 cm², what is ½ of the rectangle’s area? 20 cm² A = 40 cm² A = 20 cm²

A = 64 cm² The area of this parallelogram is 64 cm². If you divide this parallelogram in half, what two shapes do you see? A = 64 cm²

A = 64 cm² A = 32 cm² The area of this parallelogram is 64 cm². If you divide this parallelogram in half, what two shapes do you see? Triangles So if the parallelogram’s area is 64 cm², what is ½ of the parallelogram’s area? 32 cm² A = 64 cm² A = 32 cm²

Area A = 8 cm × 5 cm A = 40 cm² A = ½ × 8 cm × 5 cm A = 4 cm × 5 cm A Since triangles are ½ of a rectangle or parallelogram, the formula for finding the area of triangles is A = ½bh. A = 8 cm × 5 cm A = 40 cm² A = ½ × 8 cm × 5 cm A = 4 cm × 5 cm A = 20 cm²

Area A = 8 cm × 8 cm A = 64 cm² A = ½ × 8 cm × 8 cm A = 4 cm × 8 cm A Since triangles are ½ of a rectangle or parallelogram, the formula for finding the area of triangles is A = ½bh. A = 8 cm × 8 cm A = 64 cm² A = ½ × 8 cm × 8 cm A = 4 cm × 8 cm A = 32 cm²

Area of a Triangle ½ A = × 6 cm × 3 cm A = 3 cm × 3 cm A = 9 cm² ½ A = If you know the base (b) and the height (h) of a triangle, you can use a formula to find its area. If you multiply the ½ × b × h, you get the area (A). A = ½ × b × h or A = ½bh ½ A = × 6 cm × 3 cm A = 3 cm × 3 cm A = 9 cm² ½ A = × 4 cm × 5 cm A = 2 cm × 5 cm A = 10 cm² A = ½ × 6 cm × 7 cm A = 3 cm × 7 cm A = 21 cm² © 2007 M. Tallman

( ) 4 x 3 x 2 = 24 (4 × 3) × 2 = 4 × (3 × 2) Associative Property The way the factors are grouped does not change the product. The associative property can make finding the area of a triangle easier! ( ) 4 x 3 x 2 = 24 (4 × 3) × 2 = 4 × (3 × 2)

A = ( ) ½ × b × h (½ × b) × h = ½ × (b × h) = (½ × h) × b Associative Property The way the factors are grouped does not change the product. The associative property can make finding the area of a triangle easier! A = ( ) ½ × b × h (½ × b) × h = ½ × (b × h) = (½ × h) × b Group the factors in which ever way that makes the problem easier to solve.

Use the formula A = ½bh to find the area of the triangle. (½ × 8 ft) × 9 ft A = 4 ft × 9 ft A = 36 ft²

Use the formula A = ½bh to find the area of the triangle. 14 yd 20 yd A = (½ × 20 yd) × 14 yd A = 10 yd × 14 yd A = 140 yd²

Use the formula A = ½bh to find the area of the triangle. (½ × 16 m) × 9 m A = 8 m × 9 m A = 72 m²

Use the formula A = ½bh to find the area of the triangle. ½ × 7 in × 10 in A = 7 in × 5 in A = 35 in²

Use the formula A = ½bh to find the area of the triangle. 6 mm 11 mm A = ½ × (11 mm × 6 mm) A = 11 mm × 6 mm A = 33 mm²

Find the Area A = 36 units²

Find the Area A = 27.5 units²

Find the Area A = 24 units²

Find the Area A = 20 units²

Find the Area A = 9 units²

Find the Area A = 16 units²

Find the Area A = 21 units²

Find the Missing Measurement A = 24 mm² 24 mm² × 2 = 48 mm² 48 mm² ÷ 8 mm = 6 mm 8 mm b 6 mm

Find the Missing Measurement A = 59.5 ft² 8.5 ft h 14 ft 59.5 ft² × 2 = 119 ft² 119 ft² ÷ 14 ft = 8.5 ft

Find the Missing Measurement A = 54 in² 9 in 12 in b 54 in² × 2 = 108 in² 108 in² ÷ 9 in = 12 in

Find the Missing Measurement A = 40.25 ft² h 11.5 ft 7 ft 40.25 ft² × 2 = 80.5 ft² 80.5 ft² ÷ 7 ft = 11.5 ft

Find the Missing Measurement A = 48 yd² 48 yd² × 2 = 96 yd² 96 yd² ÷ 12 yd = 8 yd 12 yd 8 yd b