The area of a square that has a side-length of 1 cm is 1 square
centimetre (or 1 cm2). To find the area of a rectangle by
the method of counting squares, we divide the rectangle into small squares
of one centimetre side-length .
Consider a rectangle of length 5 cm and width 3 cm.
Using the method of counting squares, we find that the area of the
rectangle is 15 cm2.
Clearly, the rectangle contains 3 rows of 5 squares. Therefore:
This suggests that:
The area of a rectangle is equal to its length multiplied by its
width. That is:
Using the pronumerals A for area, l
for length and w for width, we can write
it simply as:
This is the formula for the area of a rectangle.
Example 2
Find the area of a rectangular field 20 m long and 10 m wide.
Solution:
Note:
To find the area of a region enclosed within a plane
figure, draw a
diagram and write an appropriate formula. Then substitute the given
values and use a calculator, if necessary, to obtain the required area.
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