Area of a Trapezoid
(KS3, Year 7)
In this formula, b1 and b2 are the lengths of the bases of the trapezoid and h is the height of the trapezoid. The image below shows what we mean by the lengths of the bases and the height:
How to Find the Area of a Trapezoid
Finding the area of a trapezoid is easy.Question
What is the area of a trapezoid with bases of length 3 cm and 5 cm and a height of 2 cm, as shown below?Step-by-Step:
1
Start with the formula:
Area = ½(b1 + b2)h
Don't forget: ½(b1 + b2)h = ½ × (b1 + b2) × h
2
Substitute the length of the bases and the height into the formula. In our example, b1 = 3, b2 = 5 and h = 3.
Don't forget: Calculate what's in the brackets () first (using the order of operations). In our example, (3 + 5) = 8.
or: ½ × a number = 0.5 × a number = a number ÷ 2.
Area = ½ × (3 + 5) × 2
Area = ½ × (8) × 2
Area = 8 cm2
Answer:
The area of a trapezoid with bases of length 3 cm and 5 cm and a height of 2 cm is 8 cm2."Find the Area" Widget
Here is a widget to help you learn the formulas to find the areas of different shapes.- Click on the shape you're learning about.
- Click on the pad to start.
- Follow the instructions in the bottom-left corner.
- On the last click, the formula, workings, and answer will appear in the yellow box.
- Enjoy!
I Say Trapezoid, You Say Trapezium
The shape is called a trapezoid in North America. In English speaking countries outside North America, a trapezoid is called a trapezium.What Is a Trapezoid?
A trapezoid is a four-sided flat shape with straight sides. It has a pair of opposite sides which are parallel.A Note on Units
The area of a trapezoid is a length times a length, so we say its dimension is length2. (All areas are lengths squared). This affects the units used. If the lengths of a rectangle are in cm, the area is in cm2. If the lengths are in inches, the area is in inches2.Worksheet
This test is printable and sendable