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Example 5: Find the perimeter of a square in which each side is 4 cm. 4 cm
Solution: Here, side of the square = 4 cm.

Perimeter = 4 × side = 4 × 4 cm = 16 cm 4 cm
Thus, the perimeter of the square is 16 cm.

Example 6: Find the side of a square sheet whose perimeter is 32 cm.

Solution: Given, perimeter of a square sheet = 32 cm
Perimeter of a square = 4 × side

Therefore, 32 cm = 4 × side.
32
Thus, the side of the square sheet = = 8 cm
4
Example 7: If the cost of framing a picture is `3 per cm, then find the
cost of framing a square picture whose side is 32 cm long.

Solution: Here, length of the side of a picture = 32 cm.
Perimeter of a square = 4 × side

= 4 × 32 cm = 128 cm
Now, the cost of framing a picture = `3 per cm.

Therefore, the total cost of framing the picture = 128 × `3 = `384.

Think Tank Critical Thinking
What is the perimeter of your Maths textbook and notebook? Which has a greater
perimeter and by how much?

perimeter of a triangle

In the given figure, ABC is a triangle whose sides are AB, BC and CA. A

Perimeter of DABC = AB + BC + CA

Perimeter of a triangle = Sum of its sides B C

Example 8: Find the perimeter of a triangle whose sides are 4 cm, 7 cm and 8 cm,
respectively.

Solution: Perimeter of the triangle = Sum of all its sides
= (4 cm + 7 cm + 8 cm) 7 cm 4 cm

= 19 cm

Example 9: Find the perimeter of an isosceles triangle in which each 8 cm
of the equal sides is 6 cm and the third side is 5 cm.
Solution: Perimeter of the given triangle = Sum of all its sides 6 cm 6 cm

= (6 cm + 6 cm + 5 cm)
= 1 7 c m . 5 cm

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