Chapter 9 Measurement;: Length And Area Worksheet Page 6
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MEASUREMENT: LENGTH AND AREA (Chapter 9)
B
PERIMETER
In English the word perimeter refers to the boundary of a region.
For example:
² the boundary line of a hockey field is the playing perimeter
² the boundary of a prison is protected by a perimeter fence.
However, in mathematics the word perimeter refers to the distance around a figure.
The perimeter of a closed figure is a measurement of the distance around the boundary of the
figure.
The perimeter of a polygon can be found by adding the lengths of its sides.
Example 4
Self Tutor
Find the perimeter of these polygons:
a
b
c
12 cm
6 cm
9 cm
10 cm
11 cm
a
Perimeter
b
Perimeter
c
Perimeter
= 6 + 3 + 6 + 3 units
= 9 + 10 + 12 cm
= 11 + (3 £ 6) cm
= 18 units
= 31 cm
= 11 + 18 cm
= 29 cm
We can derive formulae for the perimeters of common quadrilaterals:
SQUARES AND RHOMBUSES
All 4 sides are equal in length.
perimeter = 4 £ side length
s
s
P = 4s
So,
RECTANGLES, PARALLELOGRAMS, AND KITES
These polygons have 2 pairs of
sides of equal length.
perimeter = a + b + a + b
a
a
a
b
b
b
P = 2(a + b)
So,
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