Use the following formulae to work out the areas of these shapes:

**Rectangle**

We need to know:

- the **base **length

- the perpendicular **height **from the base to the top.

**Area of rectangle = base x height**

**Parallelogram**

We need to know:

- the **base **length

- the perpendicular **height **from the base to the top. **(not the slant height)**

**Area of parallelogram = base x height**

**Triangle**

We need to know:

- the **base **length

- the perpendicular **height **from the base to the apex.** (not the slant height)**

**Area of triangle = ½ base × height**

**or**

**Area of triangle = base × height ÷ 2**

**Example 1**

Can an area formula be used to work out the area of this parallelogram, and if so, which one?

**Answer**

This is a parallelogram.

We need to know:

- the **base **length

- the perpendicular **height **from the base to the top.* ***(not the slant height)**

We know the **base **length** **and** **the** slant height**, but **not **the **perpendicular height**.

So,** no**, we cannot use the area formula.

**Example 2**

Can an area formula be used to work out the area of this triangle, and if so, which one?

**Answer**

This is a triangle.

We need to know:

- the **base **length

- the perpendicular **height **from the base to the top. **(not the slant height)**

If we turn our heads to the left, the **base length is 12 cm **and the **perpendicular height is** **6 cm**.

*We do not need to know the slant height of 10 cm to use the formula.*

**Yes**, we can use the area formula:

**Area of triangle = ½ base × height**

Shall we do it then - just for fun!!

½ x 12 x 6 = 36 cm^{2}

Right, let's try some questions now.