Question

Q4. Perimeter of a Rectangle​

Answer 1

Answer:

the formula for perimetre of rectangle is l*b

Step-by-step explanation:

Answer 2

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Rectangles are four-sided polygons. Following are the properties of a rectangle:

(i) All the angles of a rectangle are 90º.

(ii) Opposite sides of a rectangle are always the same in size.

Perimeter of a rectangle

The perimeter of a rectangle is the total length of all the sides of the rectangle. Hence, we can find the perimeter by adding all four sides of a rectangle.

Perimeter of the given rectangle is a + b + a + b. Since opposite sides of a rectangle are always equal, we need to find the dimensions of only two sides to find the perimeter of a rectangle.

The perimeter of the above rectangle with sides ‘a units’ and ‘b units’ is:

a + b + a + b = 2a + 2b = 2 (a + b) units.

Hence, the formula for the perimeter of a rectangle = 2 × (sum of adjacent sides)

Examples of finding the perimeter of a rectangle

Example 1 :-

The two sides of the rectangle are given. What will be the perimeter of the rectangle?

Solution:-

One side of the rectangle is 2 cm and the other side is 5 cm.

We know that, the perimeter of a rectangle

= 2 × (sum of adjacent sides)

Therefore, the perimeter of the rectangle

= 2 × (5 + 2) = 2 × (7) = 14 cm

Tricky problems involving perimeter off rectangles

Type I :-

When the perimeter and only one of the sides are given.

Example 1 :-

If the perimeter of the given rectangle is 10 cm and the length of one of its sides is 2 cm. What will be the other side?

Solution:-

The perimeter of the rectangle, with one of the sides equal to 2 cm, is 10 cm.

Let the missing side be ‘a’.

We know that, the perimeter of a rectangle = 2 × (sum of adjacent sides)

10 = 2 × (2 + a) 5 = (2 + a)

a = 5 - 2 = 3 cm

Step-by-step explanation:

Hope it helps you ✌️