Area of irregular shapes

To find the area of irregular shapes, the first thing to do is to divide the irregular shape into regular shapes that you can recognize such as triangles, rectangles, circles, squares and so forth...
Then, find the area of these individual shapes and add them up!

Example #1:

Irregular shape
The figure above has two regular shapes. It has a square and half a circle

Find the area for each of those two shapes and add the results

Square

Area of the square = s2

Area of the square = 42

Area of the square = 16

Circle

Area of the circle = pi × r2

Notice that the radius of the circle is 4/2 = 2

Area of the circle = 3.14 × 22

Area of the circle = 3.14 × 4

Area of the circle = 12.56

Since you only have half a circle, you have to multiply the result by 1/2

Area of the half circle = 1/2 × 12.56 = 6.28

Area of this shape = 16 + 6.28 = 22.28

Example #2:

Irregular shape
The figure above has three regular shapes. Starting from top to bottom, it has a triangle, a rectangle, and a trapezoid

Find the area for each of those three shapes and add the results

Triangle

Area of the triangle = (base × height)/2

Area of the triangle = (3 × 4)/2

Area of the triangle = 12/2

Area of the triangle = 6

Rectangle

Area of the rectangle = length × width

Area of the rectangle = 3 × 10

Area of the rectangle = 30

Trapezoid

Area of the trapezoid = ((b1 + b2) × h)/2

Area of the trapezoid = ((3 + 5) × 2)/2

Area of the trapezoid = (8) × 2/2

Area of the trapezoid = 16/2

Area of the trapezoid = 8

Area of this shape = 6 + 30 + 8 = 44

Example #3:

The area of irregular shapes can be as challenging as this last example, so study it carefully!

Irregular shape
The figure above has 4 regular shapes. It has a triangle, two rectangles, and half a circle

Find the area for each of those 4 shapes and add the results

Rectangle

Area of the rectangle = length × width

Area of the rectangle = (12 × 16)

Area of the rectangle = 192

Since we have two of the same rectangle, the area is 192 + 192 = 384

Triangle

Notice that the longest side of the rectangle is the base of the triangle and the short side of the rectangle is the height of the triangle

So,

Area of the triangle = (base × height)/2

Area of the triangle = (16 × 12)/2

Area of the triangle = (192)/2

Area of the triangle = 96

Circle

To get the area of the half circle, we need to know the diameter

Notice that the diameter is the hypotenuse of a right triangle, so use the Pythagorean Theorem to find the length of the diameter

c2 = a2 + b2

c2 = 122 + 162

c2 = 144 + 256

c2 = 400

c = √400

c = 20

Therefore, the diameter is 20. Since the diameter is 20, the radius is 10

Area of the circle = pi × r2

Area of the circle = 3.14 × 102

Area of the circle = 3.14 × 100

Area of the circle = 314

Since you only have half a circle, you have to multiply the result by 1/2

1/2 × 314 = 157

Area of this shape = 384 + 96 + 157 = 637

Here we go! I hope these good examples were very helpful in helping you how to get the area of irregular shapes.

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