# Perimeter

• ## What is Perimeter: The outside of a 2D shape.

How to find perimeter: ADD up ALL sides of a shape.

Note: If there are no numbers located on a side, you have to decide based on the numbers given what the measument of the unknown is.

• # What is Area: The inside of a 2D shape.

## Area of a Rectangle:

Area = Base x Height

Example: Base = 8cm

Height = 5cm

A = 8cm x 5cm

A = 40 cm²

## Area of a Parallelogram

Area = Base x Height

Paralellograms have the same formula as a rectangle because parallelograms are made from rectanges. (See you notes for an example) Base = 10in

Height = 5in

A = 10in x 5in

A = 50 in²

## Area of a Triangle

Area = Base x Height ÷ 2

Note: You must ALWAYS divide this by two because it is half of a rectangle. (See your notes for an example) (you only use 5 and 9 for the perimeter, it is not needed for the area)

Base= 12 units

Height = 4 units

A = 12 x 4 ÷ 2

A = 48 ÷ 2

A = 24 units²

Area of a Trapezoid

Note: In order to find the area of a trapezoid you must decompose the shape into TWO triangles. Once you find the area of both triangles you will then add the two triangles together to get the total area of the shape.

Area = Base x Height ÷ 2   Total Area = 3 in² + 6 in² = 9 in²

# Surface Area

• What is Surface Area: The area of all sides of a 3D shape.

How do you find Surface Area: By finding the area of all shapes and then adding them together.

Net: is a flattened 3D shape. Finding the Surface are of a Net:

Find the area of each individual shapes using the correct formula and then add them all together.

Rectangular Prism: Triangular Prism 