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Subject – Mathematics
Chapter 9 – AREA & PERIMETER
Sub-topic 6 : AREA OF RECTILLINEAR/COMPOSITE FIGURE
In real life, not every plane figure can be clearly classified as a rectangle, square or a
triangle. To find the area of a composite figure which consists of more than one
shape, we need to find the sum of the area of both or all the shapes forming the
composite figure.
The main idea is to decompose the given shape into known basic shapes such
squares, rectangles and then use addition and/or subtraction to calculate the area of
the given shape.
Example:
The area of the given shape i.e. ABCDEF is calculated using 3 steps:
1) Calculate the area of the large rectangle ABWF: A1 = Length × Width = 5 × 3 = 15
2
unit
2) Calculate the area of the small rectangle CWED: A2 = CW × WE = 3 × 1 = 3 unit
2
3) Subtract the area of the small rectangle from that of the large rectangle: A = A1 -
A2 = 15 - 3 = 12 unit 2
