Std. :- 6th Sub. :- Mathematics

Chapter no. 13 Perimeter

“ A perimeter is a path that surrounds an area.” The word comes from the Greek peri (around) and meter (measure). The term may be used either for the path or its length - it can be thought of as the length of the outline of a shape. “The perimeter of a circular area is called its circumference”. In short Perimeter of a figure is the sum of the lengths of all sides of that figure

Perimeter of a Rectangle :- Formula 3 cm 1.5 cm P Q S R The Perimeter of a rectangle PQRS = Sum of lengths of all sides =l(PQ)+l(QR)+l(RS)+l(SP) =1.5 + 3 + 1.5 + 3 = 3 + 3 + 1.5 + 1.5 =2 ( length) + 2 ( breadth)

Note :- The Perimeter = 2 X length + 2 X breadth of a rectangle The Perimeter = 2 ( l + b ) of a rectangle Note :- If length & breadth of a rectangle are in Centimeters then unit of perimeter of a rectangle is cm If length & breadth of a rectangle are in Meters then unit of perimeter of a rectangle is m

The Perimeter of the rectangular playground is 390 m. The length of a rectangular playground is 120 m and its breadth is 75 m. Find its perimeter. Length of a rectangular playground = 120 m breadth of a rectangular playground =75 m The Perimeter of a rectangular playground = 2 X length + 2 X breadth = 2 X 120+ 2 X 75 = 240 +150 = 390 The Perimeter of the rectangular playground is 390 m.

Perimeter of a Square Formula :- Perimeter of a Square = 4 X length = 4 X l Ex. : Find the perimeter 0f square whose side is 12 cm . Ans. : Perimeter of a Square = 4 X lengths = 4 X l = 4 X 12 = 48 cm

Perimeter of a Triangle Formula:- Perimeter of a triangle = a + b + c b a c

Example Find the perimeter of triangle whose sides are 10cm,12cm,14cm. solution: Given : sides of triangle : a = 10 cm b = 12cm c = 14 cm Perimeter of a triangle = a + b + c = 10 + 12 + 14 = 36 cm