**Establish the formulas for areas of rectangles, triangles and parallelograms and use these in problem solving (ACMMG159)**

**LO: To find the formula for the area of rectangles, triangles and parallelograms.**

**Know:**

- the dimensions of 2-D shapes such as length and width (height)
- the properties of rectangles, triangles and parallelograms.

**Understand:**

- That formulas can be used to quickly find the area of a rectangle, triangle or parallelogram.

**Do:**

- I can find and use the formula for the area of rectangles, triangles and parallelograms.

# Rectangles, Triangles and Parallelograms

**Area of Rectangles**

**Area of Triangles**

**Area of Parallelograms**

Finding the area of rectangles is easy, all you have to do is **multiply the length by the width**.

Finding the area of triangles is easy, all you have to do is **multiply the base by the height and half** the answer.

Finding the area of parallelograms is easy, all you have to do is **multiply the base by the height**.

Another way of finding the area of a rectangle is using an **array**. An array means using rows and then adding it all up. If each row has 18 squares, if we have 6 rows, we would then go 6 x 18 which is 108 squares in total.

The reason for that is that is if I go base x height (or length x width) that is the same formula as the area of a rectangle. If you look at the picture below **each of the triangles is only half of the size of a rectangle**, which is why the formula is 1/2 x b x h.

The reason for that is that is if I cut the end piece of the parallelogram, I can slide it to the opposite side and **create a rectangle**. The area of a parallelogram is the exact same as the area of a rectangle, which is length x width (or base x height).