AreaAreaAreaArea

The size of a surface in square The size of a surface in square unitsunits

Area of a Rectangle• A rectangle with a length of 2 units and width

of 3 units has an area of 6 square units.

• The formula is ; Area of rectangle = length x width

or base x heightor base x height

length

width

2

3

1 2 3

4 5 6

Area of a Square• A square is a rectangle with all sides the

same, so the formula can be simplified.

• The formula is ; Area of square = side x side

side2

2

1 2

3 4

or side squared (side or side squared (side ) )

2

Area of a Triangle• Suppose you have a triangle that is 3 units wide

and 2 units high.– Notice what shape a triangle makes if you cut it and copy

the pieces.

• It becomes a rectangle whose area is base x height.• Notice that two whole triangles can fit into that same rectangle, meaning one triangle

is only half of the area of that rectangle

• therefore; Area of a Triangle = (base x height)/2

2

3base

height

Note that the height is always 90 degrees to the base.

Area of a Parallelogram• Suppose you have a parallelogram that is 3 units

wide and 2 units high.– Notice what shape it makes if you cut off the end and put

it on the other side.

• It becomes a rectangle whose area is base x height.• therefore; Area of a Parallelogram = base x height

2

3 base

height

Area of a Trapezoid• Suppose you have a trapezoid that is 7 units wide

on the bottom, 1 wide on the top, and 2 units high.– Notice what shape it makes if you cut off the ends

at half the height and shift upwards.

• It becomes a rectangle whose base is (top + bottom)/2.• therefore; Area of a Trapezoid = (top + bottom)/2 x height

2

7

1

4

4

Summary• Area of rectangle = length x width

length

width

Summary

• Area of rectangle = length x width• Area of square = side x side

side

side

Summary

• Area of rectangle = length x width• Area of square = side x side• Area of triangle = (base x height)/2

height

base

Summary

• Area of rectangle = length x width• Area of square = side x side• Area of triangle = (base x height)/2• Area of parallelogram = base x height

height

base

Summary

• Area of rectangle = length x width• Area of square = side x side• Area of triangle = (base x height)/2• Area of parallelogram = base x height• Area of trapezoid = (top + bottom)/2 x height

height

bottom

top