Calculate Areas of Parallelograms

Use the following formula to work out the area of a rectangle:

 

 

We must know the base length and the perpendicular height from the base to the top.

 

Area of rectangle = base × height

 

 

Now, try this with a piece of paper.

Start with a rectangle.

 

 

Cut off a right-angled triangle from the left-hand side and separate the two pieces.

The area of the two pieces together will be the same as the original rectangle.

 

Move the right-angled triangle over to the right-hand side.

The area still hasn't changed.

 

 

Join the two pieces to form a parallelogram.

The area of this parallelogram is the same as the original rectangle.

 

 

 

Area of Parallelograms

 

 

We must know the base length and the perpendicular height from the base to the top. (NOT the slant height)

 

Area of parallelogram = base × height

 

 

Example

Calculate the area of this parallelogram in cm².

 

 

Answer

To calculate the area, we must know the base length and the perpendicular height from the base to the top. (NOT the slant height)

 

The base length is 10 cm.

The slant height is 7 cm, which we do not need.

The perpendicular height is 6 cm.

 

Area = Base × Height = 10 × 6 = 60 cm²

 

Are you ready to have a go at some questions now?