SURFACE AREA AND VOLUME EXERCISE cubes each of volume 64 cm3 are joined end to end. Find the surface area of the resulting cuboid.

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SURFACE AREA AND VOLUME EXERCISE -13.1 1. 2 cubes each of volume 64 cm3 are joined end to end. Find the surface area of the resulting cuboid.

1 SURFACE AREA AND VOLUME EXERCISE cubes each of volume 64 cm3 are joined end to end. Find the surface area of the resulting cuboid. Solution: 1 The volume of each cube = 64 cm 2 3 Sides of each cube = Volume 3 Sides of each cube = 64 = 4 cm When Cubes are joined are end to end then; The length of the cuboid = 4+4=8cm Breadth of the cuboid = 4 cm Height of the cuboid = 4 cm Surface Area of the Cuboid = 2 (lb+bh+lh) =2 [(4)(8)+(4)(4)+(4)(8)]cm 2 = 2[ ] = 2[80]= 160cm 2 2. A vessel is in the form of a hollow hemisphere mounted by a hollow cylinder. The diameter of the hemisphere is 14 cm and the total height of the vessel is 13 cm. Find the inner surface area of the vessel. Solution: 2 Radius of the hemisphere = 7 cm

Radius of the Cylinder = 7 cm Height of the Cylinder = 13 7 = 6 cm Inner Surface Area of the vessel = CSA of hemisphere + CSA of Cylinder = 2πr 2 + 2πrh = 2πr(r + h) = 2 22 7 7

Solution:3 Radius of the hemisphere = 3.5 cm Radius of the Cone = 3.5 cm Height of the C0ne = 15.5 3.5 = 12 cm Slant height of the Cone l = (r 2 + h 2 ) 12.5 cm = (3.

2 Radius of the Cylinder = 7 cm Height of the Cylinder = 13 7 = 6 cm Inner Surface Area of the vessel = CSA of hemisphere + CSA of Cylinder = 2πr 2 + 2πrh = 2πr(r + h) = (6 + 7) = 572 cm2 3. A toy is in the form of a cone of radius 3.5 cm mounted on a hemisphere of same radius. The total height of the toy is 15.5 cm. Find the total surface area of the toy. Solution:3 Radius of the hemisphere = 3.5 cm Radius of the Cone = 3.5 cm Height of the C0ne = = 12 cm Slant height of the Cone l = (r 2 + h 2 ) 12.5 cm = ( )cm 2 = ( )cm 2 = Total Surface Area of the toy = CSA of hemisphere + CSA of Cone = 2πr 2 + πrl = (3.5) = = cm 2

4. A cubical block of side 7 cm is surmounted by a hemisphere. What is the greatest diameter the hemisphere can have? Find the surface area of the solid. Solution:4 Radius of the hemisphere = 3.

5)2 = 5. A hemispherical depression is cut out from one face of a cubical wooden block such that the diameter l of the hemisphere is equal to the edge of the cube.

3 4. A cubical block of side 7 cm is surmounted by a hemisphere. What is the greatest diameter the hemisphere can have? Find the surface area of the solid. Solution:4 Radius of the hemisphere = 3.5 cm Total surface area of solid = (Surface area of cubical part) + (CSA of hemisphere) (Area of the base of the hemisphere) πr = cm 2 = 6 (edge) 2 + 2πr 2 = 6(7) (3.5)2 = 5. A hemispherical depression is cut out from one face of a cubical wooden block such that the diameter l of the hemisphere is equal to the edge of the cube. Determine the surface area of the remaining solid. Solution: 5 Diameter of hemisphere = edge of the cube l Radius of hemisphere = 0.5 cm Total Surface of Solid = Surface Area of Cubical +CSA of hemisphere Area of the base of hemisphere πr 2 = 6 (edge) 2 + 2πr 2 = 6(l) 2 + π ( 1 2 )2 =6l 2 + πl2 4 cm2 = 1 4 (24 + π)l2 unit 2

6. A medicine capsule is in the shape of a cylinder with two hemispheres stuck to each of its ends (see Fig. 13.10). The length of the entire capsule is 14 mm and the diameter of the capsule is 5 mm.

Solution: 6 Radius of the Cylinder = Radius of hemisphere= Diameter of capsule 2 = 5 2 m Length of Cylinder = length of Capsule 2r = 14 5 = 9 mm Surface Area of Capsule = 2CSA of hemisphere + CSA of

4 6. A medicine capsule is in the shape of a cylinder with two hemispheres stuck to each of its ends (see Fig ). The length of the entire capsule is 14 mm and the diameter of the capsule is 5 mm. Find its surface area. Solution: 6 Radius of the Cylinder = Radius of hemisphere= Diameter of capsule 2 = 5 2 m Length of Cylinder = length of Capsule 2r = 14 5 = 9 mm Surface Area of Capsule = 2CSA of hemisphere + CSA of Cylinder = 2 2πr 2 + 2πrh = 4π ( 5 2 )2 + 2π ( 5 2 ) (9) = 25π + 45π = 70π = mm2 = 220 mm 2 7. A tent is in the shape of a cylinder surmounted by a conical top. If the height and diameter of the cylindrical part are 2.1 m and 4 m respectively, and the slant height of the top is 2.8 m, find the area of the canvas used for making the tent. Also, find the cost of the canvas of the tent at the rate of ` 500 per m2. (Note that the base of the tent will not be covered with canvas.) Solution : 7 Height of the Cylinder = 2.1 m Diameter of the Cylinder = 4 m Radius of the Cylinder = 2m

Slant height of the Cone = 2.8 m Area of Canvas = CSA of Cone + CSA of Cylinder = πrl + 2πrh = πr(l + 2h) = 22 7 2(2.8 + 2 2.1) = 44 m2 Cost of making canvas = 500 44 = Rs 22000 8.

5 Slant height of the Cone = 2.8 m Area of Canvas = CSA of Cone + CSA of Cylinder = πrl + 2πrh = πr(l + 2h) = ( ) = 44 m2 Cost of making canvas = = Rs From a solid cylinder whose height is 2.4 cm and diameter 1.4 cm, a conical cavity of the same height and same diameter is hollowed out. Find the total surface area of the remaining solid to the nearest cm2. Solution : 8 Height of the Cone = Height of the Cylinder =2.4 cm Diameter of the Cylinder = 1.4 cm, radius = 0.7cm Slant height of the Cylinder = (r 2 + h 2 ) = ( ) = 2.5 cm Total Surface Area of the remaining Solid = CSA of Cylinder + CSA of Cone + Base Area of the Cylinder = 2πrh + πrl + πr 2 = πr(2h + l + r) = [(2)(2.4)+(2.5)+0.7] = cm 2 = 18 cm 2 (approx)

9. A wooden article was made by scooping out a hemisphere from each end of a solid cylinder, as shown in Fig. 13.11. If the height of the cylinder is 10 cm, and its base is of radius 3.

6 9. A wooden article was made by scooping out a hemisphere from each end of a solid cylinder, as shown in Fig If the height of the cylinder is 10 cm, and its base is of radius 3.5 cm, find the total surface area of the article. Solution: 9 Radius of Hemisphere = Radius of Cylinder = 3.5 cm Height of Cylinder = 10 cm Surface Area of the article = CSA of Cylinder + 2(CSA of hemisphere) = 2πrh + 2πr 2 = 2πr(h + r) = [3.5+10] = 374 cm 2

EXERCISE NO:13.1. If cubes are joined end to end, the dimensions of the resulting cuboid will be 4 cm, 4cm, 8 cm. 2 lb bh lh.

EXERCISE NO:13.1. If cubes are joined end to end, the dimensions of the resulting cuboid will be 4 cm, 4cm, 8 cm. 2 lb bh lh. Class X - NCERT Maths EXERCISE NO:1.1 Question 1: cubes each of volume 64 cm are joined end to end. Find the surface area of the resulting cuboids. Solution 1: Given that, Volume of cubes = 64 cm (Edge)