Area (AQA GCSE Maths): Revision Note

Area formulas

What is area?

• Area is the amount of space within the perimeter of a 2D shape

  • For example, the size of a sports field

• Area is calculated using lengths in two dimensions

  • Units of measure include mm², cm², m² etc

How do I find the area of a shape on a square grid?

• Count the total number of whole squares inside the shape

  • You can shade or mark the squares you have counted so far

• Parts of the shape may not contain whole squares

  • Pair up half squares, or parts of squares, to form whole ones

• There will be a scale telling you how much area one square represents

  • Multiply the number of squares you have counted by this value to find the total area of the shape

Which area formulae do I need to know?

How do I find the area of a rectangle?

• The area, A, of a rectangle of length, l, and width, w, using the formula

  • 

    • Multiply together the length and the width

How do I find the area of a triangle?

• The area, A, of a triangle with base, b, and length, l, can be found using the formula

  • 

    • Multiply the length of the base (b) by the perpendicular height (h)

    • Halve the answer

• The perpendicular height may not be the length of one of the sides of the triangle

How do I find the area of a trapezium?

• The area, A, of a trapezium with parallel lengths, a and b, and perpendicular height, h, can be found using the formula

  • 

    • Add together the lengths of the parallel sides

    • Multiply the result by the distance between the parallel sides

    • Halve the answer

• You may be able to work out the area of a trapezium by splitting the shape into a rectangle and triangles if you can't remember the formula

How do I find the area of a parallelogram?

• You can find the area, A, of a parallelogram of length, l, and perpendicular height, h, by using the formula

  •  

    • Multiply the length of the base by the perpendicular height

• The perpendicular height is not a length of the parallelogram

• It is the distance between the base and its opposite side

• You can work the area of a parallelogram out by splitting the shape into a rectangle and triangles if you can't remember the formula