Page 187 - classs 6 a_Neat

 1920 
=   m 80m. EXAMPLE:11 Find the perimeter of a rectangular plot of land whose length is 1 km and
=
 24  breadth is 300 m.
Let the breadth of the field be x metres. EXAMPLE:12 Find the perimeter of a regular octagonal field whose side is 40 m.
Then, perimeter of the field = 12 x (23 + x) Im. EXAMPLE:13 A triangular park has sides 60 m, 50 m and 40 m. How much wire will be re
∴ 2(23 +x) = 80 ⇒ (23 +x) = 40 quired to put a fence round the park? What will be the cost of fencing, if the wire
⇒ x = (40-23) = 17. costs 25per metre?
Hence, the breadth of the field is 1 7 m. EXAMPLE:14 The perimeter of square park is 1,250 m. What is the length of each side?

EXAMPLE 6. Find the perimeter of a square, each of whose sides measures 3.6 cm. EXAMPLE:15 Tarun and Arun go jogging in the morning. They both jog the same distance. T arun
SOLUTION Each side of the square = 3. 6 cm. goes around a pentagonal park of side 30 m. Arun jogs around a rect angular park of
Perimeter of the square = ( 4 × side) breadth 15 m. What is the length of the park that Arun jogs around?
= (4 × 3.6) cm= 14.4 cm. EXERCISE 14-A
EXAMPLE 7. The cost of fencing a square field at ₹125 per metre is ₹8000. Find the length of
each side of the field. 1. Find the perimeter of the following figures. (All lengths are in cm.)
SOLUTION Total cost of fencing = ₹ 8000. a. A 12 B b. X 14 Y c. Q
Rate of fencing= ₹125 per metre. 8 8
  totalcos t ` 8000 P R
(total cost)₹ 8000 Length of boundary of the field =   =
 rate  `125 / m 12 11
 8000  7 7
=   m = 64m.
 125 
Let the length of each side of the field be x metres. D C W Z O 9 S
Then, its perimeter= (4×) metres.
64 2. Find the perimeter of the following triangles.
∴ 4x64 ⇒ x = = 16 a.A triangle with sides 13 cm, 9 cm and 5 cm.
4 b.An equilateral triangle with side 7 cm.
Hence, the length of each side of the field is 16 m. c.An isosceles triangle with two equal sides of 9 cm each and the third side of 6 cm
EXAMPLE 8. Find the perimeter of an equilateral triangle with each side measuring 5.8 cm. 3. Find the sides of the following figures whose perimeters are given.
SOLUTION Length of each side of the triangle = 5.8 cm. a.The side of a regular pentagon whose perimeter is 60 cm.
∴perimeter of the triangle= (3 × 5.8) cm = 17.4 cm. b.The side of a regular septagon whose perimeter is 63 cm.
EXAMPLE 9. Find the perimeter of a regular hexagon having each side equal to 6.5 cm. c.The side of a regular decagon whose perimeter is 200 cm.
SOLUTION Length of each side of the given hexagon = 6.5 cm. 4. A rectangular painting of 28 cm length and 12 cm breadth has to be framed. What will be the cost of framing
∴ perimeter of the hexagon = (6 × 6.5) cm = 39 cm.
it, if the wood strip costs ₹15 per cm?
5.Anita takes her pet dog for a walk around a square park. The side of the square is 25 m. How many metres
EXAMPLE:10 does she cover in 4 rounds of the park?
6.Raj takes 4 rounds of a rectangular park of length 60 m and breadth 15 m and Rani takes 3 rounds of a square
D B park whose side is 35 m. Who covers more distance and by how much?

7. How many trees can be planted at a distance of 8 m each around a rectangular field whose length is 8. 150 m
A C and breadth 90 m? A park is in the form of a regular hexagon of side 35 m. Find the cost of fencing it at the
rate of B.50 per metre.
E C 8, The cost of making a boundary line with paint around a square field is ₹1.250 at the rate of .₹25 per metre.
Find the length of the side of the field.
F D 9. After walking 3 times along the boundary of a triangular park with equal sides, Manpreet finds that he has

walked 2,250 m. Find the length of each side of the park.
A B E