Lets Talk Triangles Parallelograms These are parallelograms Area

Let’s Talk Triangles & Parallelograms

These are parallelograms!

Area of a Parallelogram quadrilateral A parallelogram is a ________ whose opposite sides are _____. parallel Area of a parallelogram = Since a rectangle is a type of parallelogram, the area formula is exactly the same!!

Let’s talk about height for a moment…

What is the height of each parallelogram? 4 cm 5 cm 4 ft 8 ft 13 cm 5 ft 2 in 12 in 9 in

Area of a parallelogram: 1. Which measurements will we use? h = 4 ft b = 8 ft A = bh 5 ft 4 ft 8 ft 2. Fill in the formula (4)(8) 3. Write your answer and label your units. 5 ft is not the height!! We won’t use this in our area calculation!

Area of a parallelogram: 1. Which measurements will we use? h = 8 ft b = 20 ft 2. Fill in the formula (8)(20) 3. Write your answer and label your units. A = bh 12 ft 8 ft 20 ft

Area of a parallelogram: 1. Which measurements will we use? h = 6 in b = 5 in 2. Fill in the formula (6)(5) 3. Write your answer and label your units. A = bh 7 in 6 in 5 in

Calculate the area: 1) 5 ft 8 ft 2) 3) 7 ft 1. 5 in 2. 5 in 10. 05 cm 3. 4 cm 6. 5 cm

Let’s examine something… A triangle can be thought of as half of a parallelogram.

Riddle me this… We just calculated how to find the area of a parallelogram. A = bh If a triangle is simply half of a parallelogram, then… What would be the formula for the area of a triangle?

If we have a parallelogram… A = bh 8(3) = 24 2 ft 3 ft 4 ft 8 ft What is the area of just this triangle?

Area of a triangle AREA OF A TRIANGLE Words Triangle: The area A of a triangle is onehalf the base length b times the height h. Numbers 1 A = 2 (8)(4) = 16 units 2 Formula

Area of a triangle: 5 ft 1. Which measurements will we use? h = 4 ft b = 8 ft 4 ft 8 ft 2. Fill in the formula 1 (4)(8) 2 3. Write your answer and label your units. 1 (32) 2

Area of a triangle: 1. Which measurements will we use? 12 in h = 10 in b = 15 in 10 in 15 in 2. Fill in the formula 1 (10)(15) 2 3. Write your answer and label your units. 1 (150) 2

Area of a triangle: 1. Which measurements will we use? h = 5 cm b = 12 cm 14 cm 6 cm 12 cm 2. Fill in the formula 1 (5)(12) 2 3. Write your answer and label your units. 5 cm 1 (60) 2

Area of a triangle: 1. Which measurements will we use? h = 6 ft b = 11 ft 14 ft 6 ft 11 ft 2. Fill in the formula 1 (6)(11) 2 3. Write your answer and label your units. 1 (66) 2

Calculate the area: 1) 5 in 3 in 12 in 2) 2. 3 ft 4. 5 ft 3) 8. 7 cm 4. 2 ft 7. 2 cm 6. 2 cm 1. 5 cm

Keypoint! The base of a triangle is not always the bottom side!!!

Let’s try one! Graph and find the area of the figure with the given vertices. (– 2, 2), (4, 2), (0, 5) Area of a triangle A = 1 bh 2 (0, 5) (– 2, 2) (4, 2) 6 Substitute for b and h. = 1 • 6 • 3 2 = 9 units 2