Question

Find them perimeter of rectangle using the formula L*B

L = 12.5 cm, b = 6.8 cm​

Answer 1

The perimeter of a rectangle is defined as the sum of all the sides of a rectangle. For any polygon, the perimeter formulas are the total distance around its sides. In case of a rectangle, the opposite sides of a rectangle are equal and so, the perimeter will be twice the width of the rectangle plus twice the length of the rectangle and it is denoted by the alphabet “p”. Let us derive the formula for its perimeter and area.

Suppose a rectangle has length and width as b and a, respectively.



From the definition of the perimeter we know, the perimeter of a rectangle, P = 2 ( a+b) units

where

“a” is the length of the rectangle

“b” is the breadth of the rectangle

Derivation

Since the perimeter is equal to the sum of all the sides of the polygon. Hence, in the case of a rectangle, the perimeter (P) is;

P = sum of all its four sides

P = a + b + a + b   (Opposite sides of rectangle are equal)

P = 2(a + b)

Hence, derived.

Therefore,

Perimeter of a rectangle = 2(Length + Width) square units

Now let us write the formula for the area of a rectangle, with respect to same above given figure;

Area of a rectangle = Length × Width = a × b

Solved Problems

Q.1: Find the perimeter of a rectangle whose length and width is 5 cm and 10 cm, respectively.

Solution: Given:

Length = 5 cm and Width = 10 cm

We know,

The perimeter of a rectangle = 2(length + width)

Substitute the value of length and width here,

Perimeter, P = 2(5 + 10) cm

P = 2 x 15 cm

Therefore, the perimeter of a rectangle = 30 cm

Q.2: Find the perimeter of a rectangle whose length and breadth are 12 cm and 15 cm, respectively.

Solution:

Given:

Length = 12 cm and Breadth = 15 cm

We know,

The perimeter of a rectangle = 2(length + width)

Substitute the value of length and width here,

Perimeter, P = 2(12 + 15) cm

P = 2 x 27 cm

Therefore, the perimeter of a rectangle = 54 cm

Answer 2

$\rm \: we \: know: \\ \\ \rm \: perimeter = 2(l + b) \\ \\ \implies \rm{}perimeter = 2(12.5 + 6.8) \\ \\ \implies \rm{}perimeter = 2(19.3) \\ \\ \implies \underline{ \boxed{\rm{}perimeter = 38.6}}$