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Chapter Overview
Learning Goals
Learning Goals
Maths
Summary
The perimeter and area of triangles and quadrilaterals can be calculated with their own formula. These formulae can also be applied to finding the area and perimeter of compound shapes.
The perimeter of a shape is the sum of the lengths of the outer sides of the shape.
The area of a shape tells you the size of the surface of the shape.
These are the following formulae you need to know.
shape | formula | illustration |
Triangle | $\text{Area}=\frac{1}{2}\times\text{base}\times\text{perpendicular\,height}$
$A=\frac{1}{2}bh$ | |
Square | $\text{Area}=\text{length}^2$
$A=x^2$ | $x$ |
Rectangle | $\text{Area}=\text{length}\times\text{width}$
$A=lw$ | |
Parallelogram | $\text{Area}=\text{base}\times\text{perpendicular\,height}$
$A=bh$ | |
Trapezium | $\text{Area}=\frac{1}{2}\times(a+b)\times\text{height}$, $A=\frac{1}{2}(a+b)\times h$ where $a$ and $b$ are the lengths of the two parallel sides. |
You can use the formulae for the areas and perimeters of triangles and quadrilaterals to solve problems involving more complex shapes.
In the diagram below, let $a=5m,b=9m,c=4m$