Calculate Areas: Parallelograms

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

 

We must know:

• the base length
• 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
• 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 th area, we must know:

• the base length
• 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