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Perimeter- The sumof length of all sides of a figure is called perimetey., ° Perimeter of triangle=Sum ofthree sides of a triangle is its perimete,, , Perimeter = Sum ofall sides or three sides, 34+44+5=12cm., , Perimeter of rectangle, Sum of 4 sides or Perimeter = 2 (I+ b) unit, , Perimeter of square = 4xside orside x4, , Example-1 Findthe perimeter ofa triangle whose sides are 4.5m, 4cm and 6 om, , Solution Perimeter ofatriangle = sum of 3sides, 4+4.5+6 cm =14.5cm vem, Perimeter of the triangle = 14.5cm, , Example -2 Find the perimeter of square whose side is 7 cm., , Solution Side=7cm_, Perimeter of square = 4 x side, 4x7=28cm, , Perimeter of square = 28 cm, , Find the perimeter of the following figures., , (ii) 8cm
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(v), , 6cm, , , , , , , , 4cm, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , 5cm 5cm, 3cm 3cm 5cm, (vii) Son (viii), 2cm 2cm-4, 6 cm| 4cm, 2cm tom, Find the perimeter of a triangle of sides are 14.5 cm, 15.6 and 16 cm., , The sides of some triangles are given. Find the perimeter., , (a) 5.2cm,7.8cm and4cm (b) 3.7cm,4.3cm and 5.8cm, , (c) 8cm,10cm, andi0cm (d) 6cm,6cmand6cm, , The sides of some squar are given. Find the perimeter., , (a) side =15cm _—(b)side=6.4m (c)side = 63cm (d) side =90m, The dimensions of some rectangles are given. Find the perimeter., , (a) length= 6.5cm,breadth=4cm. (b) length=125m, breadth = 80m., , Mohini wants to put a lace around a rectangular gift of length 14 cm and, breadth 5 cm. Find the length of the lace required., , Find the perimeter equilateral triangle whose side is 13 cm., , The length of the side a square garden is 160 metres. How much will it cost to, fence the garden at % 9 per metre ?, , Afield is 140 m long and 80m wide. Rohan goes jogging around it 6 time. How, much distance does he cover?, , Neetigya runs along the side of a square park which is 90 metres long. If she |, , Covers 4 cm in one step. How many steps will she take to run one round the, Park.
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When we place a book or anything on the plane surface. It covers som,, surface of the plane. Thus we can say every object covers some space of the, , surface of plane., , Observe the following figures carefully., , Therefore, the space of the plane covered by the closed figure is called the, , area of the figure. The region enclosed by each figure which is shown by shaded, portion is the area of that figure. (Unit ofarea = Square Unit), , Formula for calculating the area, , Area of triangle = 4 x Base x Height, , (a= 4 xbxh), Area of rectangle = Length x Breadth, (a= Ixb), Area of square = side x side, (a= side x side ), or a= Side’, Examples 1. Find the area ofa triangle whose base is 6 cm and heightis 9 cm., Solution Base of the triangle = 6cm, Height of the triangle = 9cm, Area of the triangle = 1yxbxh, , Area of the triangle = 27 cm’
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mple 2. Find the base ofa triangle whose area is 36 cm’ and heightis 6, ee cm., golution , area ofthe triangle = 36cm z z, , Base of the triangle =, Height of the triangle = 6cm, ofthe triangle = area x 2, pass height, 8 height of the triang|, Ae = 12, 1, , Base of the triangle = 12cm, , Example 3. Find the area of a square of each side 7 cm., , Solution , Side of asquare = 7cm, Area of asquare = (side)’orsidexside, 7x7=49, , Area of a square is 49 cm”, , Example 4. The area of squareis 81 m?. Find out the side of square., , Solution , , , Let the side be x m. Prime Factors of 81, Areaofasquare = 81 m?, (side)? = Area | 3181, x? = 8 327, x = FF 3/9, or x = 9 SNES Eze, Hence, Side of square is 9 m. 1, , , , So 3x3x3x3, 3°x3°=9°
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dthe area of a park of length 30 m and breadth 22m., , , , Example 5. Fin, , Solution- Length of the park = 30m, Breadth of the park = 22m, Area of the park = Ixb, , 30 x 22, , = 660m, , Area of the park is 660 m, , Example 6. The area of agarden is 360m and breadth is 12m. Find the length, , of the garden., Solution- Areaofgarden = 360m, Breadth of garden = 12m, Length of garden = area, breadth, 30, ~ 42, 7 °°, , Length of garden os 30 m., , Note - Breadth of rectangle = length, , Exercise - 17.2 9 : ae |, , 1. Find out the area of the following triangle whose measures are given., , 4em, height=6cm (b)base=12cm, height=10cm, , ", , (a) base, (c) base = 7cm, height=4cm (d)base=5cm, height=9 cm, , 2. Findoutthe area of the following square whose side is given., (a) 12cm (b) 15cm (c) 18.5cm, (d) 25m (e) 32.5m (f) 42.35m
