# Area and perimeter of triangles

### Area and perimeter of triangles

#### Lessons

In this lesson, we will learn:

• The basic properties of the shape of the triangle
• How to understand and calculate the perimeter of a triangle
• How to understand and calculate the area of a triangle

Notes:

• A triangle is a 2D shape with 3 straight sides and 3 angles that add up to 180°
• There are different types triangles (classified by side lengths or angle size), but it does not change the formulas for area and perimeter.

• The perimeter is the exact distance around the shape.
• Perimeter is a 1D (one-dimensional) quantity
• It uses units such as meters (m, cm, mm, km), miles (mi), yards (yd), or inches and feet (in and ft)

• For triangles, the formula is written as:
• Ptriangle = side1 + side2 + side3

• This formula does not change for different types of triangles

• The area is the space that is covered by the shape.
• Area is a 2D (two-dimensional) quantity
• It uses squared units such as square meters (m2, cm2, mm2, km2), square miles (mi2), square yards (yd2), or square inches and feet (in2 and ft2)

• For triangles, the formula is written as:
• Areatriangle = $\large \frac{b \, \times \, h} {2}$
• Where $b$ is base, and $h$ is height

• This formula does not change for different types of triangles, but you do need to keep in mind how to find the triangle’s height
• The triangle’s base is any of the three straight sides
• The triangle’s height is found by placing the chosen base as the flat bottom, and then drawing a perpendicular line from that until the highest point (vertex); it can also be called the triangle’s altitude

• Introduction
Introduction to Area and Perimeter of Triangles:
a)
What are the basic properties of a triangle?

b)
How do you calculate the perimeter of a triangle?

c)
How do you calculate the area of a triangle?

• 1.
Perimeter of Triangles
Calculate the perimeter of each triangle.
a)

b)

c)

• 2.
Area of Triangles
Calculate the area of each triangle.
a)

b)

c)

• 3.
Perimeter and Area of Compound Triangle Shapes
Calculate the perimeter and area of each compound shape. Break down the complex shapes into components (triangles and rectangles) first!
a)

b)

c)

• 4.
Triangles Word Problem
The side of a skateboard ramp is a right triangle. What is the perimeter and area of the side of a skateboard ramp that has the following measurements: base=20m, height=15m, slope=25m