Perimeter of a Square: formula & Solved questions

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Jasmine Grover

Education Journalist | Study Abroad Lead

The perimeter of a square is the total distance at the boundaries or outside the square. The perimeter of any closed figure is calculated by finding the sum of all the sides. A Square is a quadrilateral with four equal sides, thus, the sum of the length of all four sides will be the perimeter of a square. Since all of its sides are equal, the perimeter is taken to be four times the length of one side.

In other words, the perimeter is the distance around a closed figure. It is the length of a shape or path that encompasses it. Therefore, the closed figure, being a square, its perimeter will be;

P = 4 × side

Or P = 4a, where a will be the side of square

Key terms: Perimeter, Square, Sum of lengths, Properties of square, perimeter Formula, Diagonals


What is a square?

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Square is a rectangular quadrilateral with four equal sides and equal angles, with each angle being 90°. It is a plane figure with four equal and parallel sides. It can even be referred to as a rectangle, with the two adjacent sides being equal. If the vertices of a square are A, B, C, and D, then the figure would be denoted as ABCD. 

Square

Square

Also read: Types of polygon


Properties of a square

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A square is a 4-sided closed figure. The properties of a square are used in many applications. The following mentioned are some important properties of a square.

  • The diagonals of a square bisect each other.
  • The diagonals of a square are perpendicular to each other.
  • All four sides of a square are of equal length.
  • Opposite sides of a square are both equal and parallel.
  • All the four angles of a square are equal and right-angled. (Square is 360°/4 = 90 degrees)
  • The diagonals of a square are equal in length.

Also read: Area of square


Perimeter of square formula

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Since, the perimeter is the distance around a closed figure, the perimeter of a square will be the sum of its four sides. Perimeter of square= side+side+side+side

But, because all the four sides of a square are equal, the formula for its perimeter will be;

P= a×a×a×a

P= 4×a

P= 4a, where a is the length of side

Or

P = 4 × side

Perimeter of square

Perimeter of square

For example, let us calculate the perimeter of a square of each side 7 cm.

The formula for the perimeter of a square is P = 4a, where a = length of each side of square.

Therefore, the perimeter of the square is, P = 4 x 7cm = 28cm

Also read: Perimeter and Area of circle 


Things to remember

  • Square is quadrilateral with equal sides and angles.
  • The diagonals of a square are equal and bisect each other at 90 degrees.
  • The perimeter of a square is given by 4×side.
  • A square has all the properties of a rectangle, except that it has equal sides.
  • All the four angles of a square are 90 degrees.
  • A square can be considered as a regular polygon.

Also read: Parallel perpendicular axes theorem


Solved questions

Ques. Find the perimeter and area of a square with length 5m. [3 marks]

Ans. Given that

Side= 5m

the perimeter and area of a square with length 5m

Area= side2 = 5×5= 25m2

Perimeter= 4× side= 4×5= 20m

Ques. What will be the perimeter of the square if the length of each side is 16ft? [3 marks]

Ans. Length of each side= 16ft

Perimeter of square= 4a

4×16= 64ft

Therefore, the perimeter of the square will be 64ft.

Ques. The perimeter of a square is 24cm. If the perimeter is increased by 4cm, what would be the length of each side? [4 marks]

Ans. Original perimeter of square= 24cm

New perimeter= 24+4= 28cm

Perimeter= 4× length of side of square

Let the length of side be k

Perimeter= 4×k

28= 4×k

k= 28/4= 7

Thus, the side of square will be 7cm

Ques. The area of a square box is 225 cm². Find the perimeter of the box. [3 marks]

Ans. Area of square box= 225 cm²

Let the side of square be s

Area= s2

225= s2

s= 15 cm

Thus, the perimeter of box will be

P= 4×s

P= 4×15= 60 cm

Ques. Find the perimeter of the square with length of 7.8 meters. [2 marks]

Ans. Side of square= 7.8m

Perimeter of square= 4×side

P= 4×7.8= 31.2m

Thus, the perimeter of the square is 31.2 m.

Ques. The side of a square frame is 6cm. What will be the total cost, if the cost per cm is Rs.3? [3 marks]

Ans- Side of square frame= 6 cm

Perimeter of frame= 4×side

P= 4×6= 24 cm

Cost per cm = Rs.3

Total cost= P× Rs.3

24×3= Rs.72

Thus, the cost of framing will be Rs.72

Ques. Arjun wants to fence three sides of a square field of length 14m. Find the cost of fencing at the rate of Rs.100 per metre. [3 marks]

Ans. Side of square field= 14 m

Perimeter of square= 4×side

4×14= 56m

Length of fence required (excluding one side) = 56-14 = 42m

Cost of fencing= 42× Rs.100= Rs.4200

Ques. If the area of a square field is 324 m², find the perimeter of the field. [3 marks]

Ans. Area of square= 324 m2

Let the side of square be s

Area = s2

324= s2

s= 18 m

Perimeter of square field= 4s

4×18= 72 m

Ques. If the length of the diagonal of a square is 50 cm, find the perimeter of square. [5 marks]

Ans- Let each side of the square be k cm.

k2+k2= (50)2 [Using Pythagoras Theorem]

2k2 = 2500

k2 = 1250

k= √1250 =√2×5×5×5×5

k= 5 × 5 × √2 = 25√2

Thus, the side of square = 25√2 cm

Perimeter of the square = 4 × side = 4 × 25√2 = 100√2 cm

Ques. A wire is in the shape of a square of length 10cm. If the wire is rebent in the form of a rectangle of length , find the length of it. [5 marks]

Ans- Side of square= 12 cm

Length of the wire = Perimeter of the square = 4 × side = 4 × 12 cm

= 48 cm

Length of the rectangle, l = 14 cm. Let b be the breadth of the rectangle.

The Perimeter of the rectangle will be equal to the length of the wire.

Perimeter of the rectangle = 2 (l + b)

Thus, 48 = 2 (14 + b)

Therefore, b = 24 − 14 = 10 cm

The breadth of the rectangle will be 10 cm.

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