A trapezoid is a 4-sided flat shape with straight sides that has a pair of opposite sides parallel (marked with arrows below):
|has a pair of parallel sides|
is an isosceles trapezoid when it has equal angles from a parallel side
|is called a "trapezium" in the UK (see below)|
Play with a trapezoid:
The parallel sides are the "bases"
The other two sides are the "legs"
The distance (at right angles) from one base to the other is called the "altitude"
The Area is the average of the two base lengths times the altitude:
Area = a+b2 × h
Example: A trapezoid's two bases are 6 m and 4m, and it is 3m high. What is its Area?
Area = 6 m + 4 m2 × 3 m = 5 m × 3 m = 15 m2
The Area of Polygon by Drawing tool is helpful when you can draw your Trapezoid.
The Perimeter is the distance around the edges.
The Perimeter is the sum of all side lengths:
Perimeter = a+b+c+d
Example: A trapezoid has side lengths of 5 cm, 12 cm, 4 cm and 15 cm, what is its Perimeter?
Perimeter = 5 cm + 12 cm + 4 cm + 15 cm = 36 cm
Median of a Trapezoid
The median (also called a midline or midsegment) is a line segment half-way between the two bases.
The median's length is the average of the two base lengths:
m = a+b2
You can calculate the area when you know the median, it is just the median times the height:
Area = mh
A trapezium (UK: trapezoid) is a quadrilateral with NO parallel sides.
The US and UK have their definitions swapped over, like this:
|US:||a pair of parallel sides||NO parallel sides|
|UK:||NO parallel sides||a pair of parallel sides|