Solution; Given height of the cylinder, H = 30 cm Radius of the cylinder, r = 7 cm Height of cone, h = 24 cm Radius of cone, r = 7 cm Slant height of the cone, l = √(h2+r2) l = √(242+72) l =...
Secondary productivity is the rate of formation of new organic matter by
Option A Producers
Option B Parasites
Option C Consumers
Option D Decomposers
The correct answer is Option C Consumers. This is because - Primary productivity is determined by the producers that live in a given area. Secondary productivity, on the other hand, is the pace at...
Natural reservoir of phosphorus is
Option A Sea water
Option B Animal bones
Option C Rocks
Option D Fossils
The correct answer is Option C Rocks. This is because - The largest reservoir of phosphorus is in sedimentary rocks..
A circus tent is in the shape of a cylinder surmounted by a cone. The diameter of the cylindrical portion is 24 m and its height is 11 m. If the vertex of the cone is 16 m above the ground, find the area of the canvas used to make the tent.
Given diameter of the cylindrical part of tent, d = 24 m Radius, r = d/2 = 24/2 = 12 m Height of the cylindrical part, H = 11 m Since vertex of cone is 16 m above the ground, height of cone, h =...
Which of the following are likely to be present in deep sea water?
Option A Archaebacteria
Option B Eubacteria
Option C Blue-green algae
Option D Saprophytic fungi
The correct answer is Option A Archaebacteria. This is because Archaebacteria are distinguished from other bacteria by the presence of branched chain lipids in their cell membrane, which allows them...
The colonies of recombinant bacteria appear white in contrast to blue colonies of non- recombinant bacteria because of
Option A Non-recombinant bacteria containing beta-galactosidase
Option B Insertional inactivation of alpha-galactosidase in non-recombinant bacteria
Option C Insertional inactivation of alpha-galactosidase in recombinant bacteria
Option D Inactivation of glycosidase enzyme in recombinant bacteria
The correct answer is Option C Insertional inactivation of alpha-galactosidase in recombinant bacteria. This is because - Lysozyme breaks down bacterial cell walls. Cellulase is a...
Which of the following is not correctly matched for the organism and its cell wall degrading enzyme?
Option A Bacteria – Lysozyme
Option B Plant cells – Cellulase
Option C Algae – Methylase
Option D Fungi – Chitinase
The correct answer is Option C Algae - Methylase. This is because - Bacterial cell walls are destroyed by lysozyme. Cellulase is an enzyme that breaks down cellulose in plant cell walls. In fungus,...
DNA fragments generated by the restriction endonucleases in a chemical reaction can be separated by
Option A Centrifugation
Option B Polymerase chain reaction
Option C Electrophoresis
Option D Restriction mapping
The correct answer is Option C Electrophoresis. This is because - DNA fragments formed by restriction endonucleases in a chemical reaction can be separated by gel electrophoresis using an agarose...
A good producer of citric acid is
Option A Aspergillus
Option B Pseudomonas
Option C Clostridium
Option D Saccharomyces
The correct answer is Option A Aspergillus. This is because - Aspergillus niger (a fungus) is a producer of citric acid.
Which of the following Bt crops is being grown in India by the farmers?
Option A Maize
Option B Cotton
Option C Brinjal
Option D Soybean
The correct answer is Option B Cotton. This is because - The Bt toxin gene has been cloned from bacteria and expressed in plants in Bt crops to give insect resistance without the use of...
The tendency of population to remain in genetic equilibrium may be disturbed by
Option A Random mating
Option B Lack of migration
Option C Lack of mutation
Option D Lack of random mating
The correct answer is Option D Lack of random mating. This is because - Allele frequencies in a population are stable and constant from generation to generation, hence the gene pool remains...
A toy is in the form of a cone of radius 3.5 cm mounted on a hemisphere of same radius. If the total height of the toy is 15.5 cm, find the total surface area of the toy.
Given radius of the cone, r = 3.5 cm Radius of hemisphere, r = 3.5 cm Total height of the toy = 15.5 cm Height of the cone = 15.5 – 3.5 = 12 cm Slant height of the cone, l = √(h2+r2) l = √(122+3.52)...
A wooden article was made by scooping out a hemisphere from each end of a solid cylinder (as shown in the given figure). 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: Given height of the cylinder, h = 10 cm Radius of the cylinder, r = 3.5 cm Radius of the hemisphere = 3.5 cm Total surface area of the article = curved surface area of the cylinder +...
A cubical block of side 7 cm is surmounted by a hemisphere. What is the greatest diameter that the hemisphere can have? Also, find the surface area of the solid.
Given edge of the cube, a = 7 cm Diameter of the hemisphere, d = 7 cm Radius, r = d/2 = 7/2 = 3.5 cm Surface area of the hemisphere = 2r2 = 2×(22/7)×3.52 = 44×12.25/7 = 539/7 = 77 cm2 Surface area...
A pen stand made of wood is in the shape of a cuboid with four conical depressions to hold pens. The dimensions of the cuboid are 15 cm by 10 cm by 3.5 cm. The radius of each of the depression is 0.5 cm and the depth is 1.4 cm. Find the volume of the wood in the entire stand, correct to 2 decimal places.
Solution: Dimensions of the cuboid = 15 cm× 10 cm × 3.5 cm Volume of the cuboid = 15×10×3.5 = 525 cm3 Radius of each depression, r = 0.5 cm Depth, h = 1.4 cm Volume of conical depression = (1/3)r2h...
16 glass spheres each of radius 2 cm are packed in a cuboidal box of internal dimensions 16 cm x 8 cm x 8 cm and then the box is filled with water. Find the volume of the water filled in the box.
Solution: Given dimensions of the box = 16 cm ×8 cm ×8 cm So volume of the box = lbh = 16×8×8 = 1024 cm3 Radius of the glass sphere, r = 2 cm Volume of the sphere = (4/3)r3 = (4/3)×(22/7)×23 =...
A cone of maximum volume is curved out of a block of wood of size 20 cm x 10 cm x 10 cm. Find the volume of the remaining wood.
Given dimensions of the block of wood = 20 cm × 10 cm× 10 cm Volume of the block of wood = 20×10×10 = 2000 cm3 [Volume = lbh] Diameter of the cone, d = 10 cm Radius of the cone , r = d/2 = 10/2 = 5...
The tendency of population to remain in genetic equilibrium may be disturbed by
Option A Random mating
Option B Lack of migration
Option C Lack of mutation
Option D Lack of random mating
The correct answer is Option D Lack of random mating. This is because - Allele frequencies in a population are stable and constant from generation to generation, hence the gene pool remains...
The given figure shows a solid trophy made of shining glass. If one cubic centimetre of glass costs Rs 0.75, find the cost of the glass for making the trophy
Solution: Given side of the cube, a = 28 cm Radius of the cylinder, r = 28/2 = 14 cm Height of the cylinder, h = 28 cm Volume of the cube = a3 = 283 = 28×28×28 = 21952 cm3 Volume of the cylinder =...
The adjoining figure shows a cuboidal block of wood through which a circular cylindrical hole of the biggest size is drilled. Find the volume of the wood left in the block.
Solution: Given diameter of the hole, d = 30 cm radius of the hole, r = d/2 = 30/2 = 15 cm Height of the cylindrical hole, h = 70 cm Volume of the cuboidal block = lbh = 70×30×30 = 63000 cm3 Volume...
Write whether the following statements are true or false. Justify your answer :
(i) The volume of a sphere is equal to two-third of the volume of a cylinder whose height and diameter are equal to the diameter of the sphere.
(ii) The volume of the largest right circular cone that can be fitted in a cube whose edge is 2r equals the volume of a hemisphere of radius r.
(iii) A cone, a hemisphere and a cylinder stand on equal bases and have the same height. The ratio of their volumes is 1 : 2 : 3.
Solution: (i)Let the radius of sphere be r. Then height of the cylinder, h = 2r Radius of cylinder = r Volume of cylinder = r2h = ×r2×2r = 2r3 Volume of sphere = (4/3)r3 = (2/3)× 2r3 = (2/3)× Volume...
The surface area of a solid sphere is 1256 cm². It is cut into two hemispheres. Find the total surface area and the volume of a hemisphere. Take π = 3.14.
Solution: Given surface area of the sphere = 1256 cm2 4r2 = 1256 4×3.14×r2 = 1256 r2 = 1256×/3.14×4 r2 = 100 r = 10 cm Total surface area of the hemisphere = 3r2 = 3×3.14×102 = 3×3.14×100 = 942 cm2...
The water for a factory is stored in a hemispherical tank whose internal diameter is 14 m. The tank contains 50 kilolitres of water. Water is pumped into the tank to fill to its capacity. Find the volume of water pumped into the tank.
Solution: Given internal diameter of the hemispherical tank, d = 14 m So radius, r = 14/2 = 7 m Volume of the tank = (2/3)r3 = (2/3)×(22/7)×(7)3 = 718.667 m3 = 718.67 m3 (approx) = 718.67 kilolitre...
A hemispherical bowl has a radius of 3.5 cm. What would be the volume of water it would contain?
Solution: Given radius of the hemispherical bowl, r = 3.5 cm = 7/2 cm Volume of the hemisphere = (2/3)r3 = (2/3)×(22/7)×(7/2)3 = 11×49/6 = 539/6 Hence the volume of the hemispherical bowl is...
Find the volume of a sphere whose surface area is 154 cm².
Solution: Given surface area of the sphere = 154 cm2 4r2 = 154 4×(22/7)×r2 = 154 r2 = (154×7)/(4×22) r2 = 49/4 r = 7/2 Volume of the sphere = (4/3)r3 = (4/3)×(22/7)×(7/2)3 = 539/3 = 179.666 = 179.67...
A cube of side 4 cm contains a sphere touching its sides. Find the volume of the gap in between.
Solution: Given side of the cube, a = 4 cm Volume of the cube = a3 = 43 = 4×4×4 = 64 cm3 Diameter of the sphere = 4 cm So radius of the sphere, r = d/2 = 4/2 = 2 cm Volume of the sphere = (4/3)r3 =...
(a) If the ratio of the radii of two sphere is 3 : 7, find :
(i) the ratio of their volumes.
(ii) the ratio of their surface areas.
(b) If the ratio of the volumes of the two sphere is 125 : 64, find the ratio of their surface areas.
Solution: (i)Let the radii of two spheres be r1 and r2. Given ratio of their radii = 3:7 Volume of sphere = (4/3)r3 Ratio of the volumes = (4/3)r13/(4/3)r23 = r13/ r23 = 33/73 = 27/343 Hence the...
A sphere and a cube have the same surface area. Show that the ratio of the volume of the sphere to that of the cube is √6 :√π
Solution: Let r be the radius of the sphere and a be the side of the cube. Surface area of sphere = 4r2 Surface area of cube = 6a2 Given sphere and cube has same surface area. 4r2 = 6a2 r2/a2 = 6/4...
The radius of a spherical balloon increases from 7 cm to 14 cm as air is jumped into it. Find the ratio of the surface areas of the balloon in two cases.
Solution: Given radius of the spherical balloon, r = 7 cm Radius of the spherical balloon after air is pumped, R = 14 cm Surface area of the sphere = 4r2 Ratio of surface areas of the balloons =...
A hemispherical brass bowl has inner- diameter 10.5 cm. Find the cost of tin-plating it on the inside at the rate of Rs 16 per 100 cm2.
Solution: Given inner diameter of the brass bowl, d = 10.5 cm Radius, r = d/2 = 10.5/2 = 5.25 cm Curved surface area of the bowl = 2r2 = 2×(22/7)×5.252 = 173.25 cm2 Rate of tin plating = Rs.16 per...
Find:
(i) the curved surface area.
(ii) the total surface area of a hemisphere of radius 21 cm.
Solution: (i) Given radius of the hemisphere, r = 21 cm Curved surface area of the hemisphere = 2r2 = 2×(22/7)×212 = 2×22×3×21 = 2772 cm2 Hence the curved surface area of the hemisphere is 2772 cm2....
Find the diameter of a sphere whose surface area is 154 cm2 .
Solution: Given surface area of the sphere = 154 cm2 Surface area of the sphere = 4r2 4×(22/7)×r2 = 154 r2 = 154 ×7/(22×4) = 49/4 r = √49/2 Diameter = 2×r = 2×√49/2 = √49 = 7 Hence the diameter of...
A shot-put is a metallic sphere of radius 4.9 cm. If the density of the metal is 7.8 g per cm3, find the mass of the shot-put.
Solution: Given radius of the metallic sphere, r = 4.9 cm Volume of the sphere, V = (4/3)r3 V = (4/3)×(22/7)×4.93 V = 493.005 V = 493 cm3 (approx) Given Density = 7.8 g per cm3 Density = Mass/...
Find the surface area of a sphere of diameter:
(i) 21 cm
(ii) 3.5 cm
Solution: (i) Given diameter of the sphere, d = 21 cm Radius, r = d/2 = 21/2 = 10.5 Surface area of the sphere = 4r2 = 4×(22/7)×10.52 = 1386 cm2 Hence the surface area of the sphere is 1386 cm2....
Find the volume of a sphere of radius :
(i) 0.63 m
(ii) 11.2 cm
Solution: (i) Given radius of the sphere, r = 0.63 m Volume of the sphere, V = (4/3)r3 = (4/3)×(22/7)×0.633 = 1.047 m3 = 1.05 m3 (approx) Hence the volume of the sphere is 1.05 m3. (ii) Given radius...
A semi-circular lamina of radius 35 cm is folded so that the two bounding radii are joined together to form a cone. Find
(i) the radius of the cone.
(ii) the (lateral) surface area of the cone.
(i)Given radius of the semi circular lamina, r = 35 cm A cone is formed by folding it. So the slant height of the cone, l = 35 cm Let r1 be radius of cone. Semicircular perimeter of lamina becomes...
In Kreb’s cycle, the conversion of oxalosuccinate into -ketoglutarate involves (1) Oxidation (2) Reduction (3) Hydration (4) Decarboxylation
Correct option: (4)Decarboxylation Solution: Oxalosuccinate is converted into α-ketoglutarate by oxidative decarboxylation during Kreb’s cycle.
The height of a cone is 30 cm. A small cone is cut off at the top by a plane parallel to its base. If its volume be 1/27 of the volume of the given cone, at what height above the base is the section cut?
Solution: Given height of the cone, H = 30 cm Let R be the radius of the given cone and r be radius of small cone. Let h be the height of small cone. Volume of the given cone = (1/3)R2H Volume of...
The adsorption of water by hydrophilic compounds like cellulose and pectin in root hair cell wall is called (1) Diffusion (2) Imbibition (3) Guttation (4) Osmosis
Correct option:(2)Imbibition Solution: Imbibition is an adsorption of water by hydrophilic compounds like cellulose and pectine in root hair cell wall.
A right triangle with sides 6 cm, 8 cm and 10 cm is revolved about the side 8 cm. Find the volume and the curved surface of the cone so formed. (Take π = 3.14)
So the height of the resulting cone, h = 8 cm Radius, r = 6 cm Slant height, l = 10 cm Volume of the cone, V = (1/3)r2h V = (1/3)×3.14×62×8 V = (1/3)×3.14×36×8 V = 3.14×12×8 V = 301.44 cm3 Hence the...
“Pusa Sadabahar” is resistant to disease. (1) Leaf curl and chilli mosaic virus (2) Leaf and stripe rust (3) Black rot (4) Curl blight black rot
Correct option :(A)(1) Leaf curl and chilli mosaic virus Solution: ‘Pusa Sadabhar’ is resistance to disease leaf curl and chilli mosaic virus of chilli. Himgiri of wheat is resistance to leaf and...
Which one of the following carbohydrates is a heteropolysaccharide ? (1) Cellulose (2) Starch (3) Glycogen (4) Hyaluronic acid
Correct option: (4)Hyaluronic acid Solultion: Hyaluronic acid is a hetropolysaccharide. It is made up of glucuronic acid and N acetyl-D-glucosamine disaccharide units.
Cambium is essential for grafting in plants because (1) Cambia of both stock and scion fuse together (2) Cambium produces new leaves (3) Cambium produces new roots (4) Cambium helps in the production of flowers
Correct option:(1)Cambia of both stock and scion fuse together Solution: Cambium is essential for grafting in plants because cambia is consists of meristematic cells of stock and scion fuse...
The perimeter of the base of a cone is 44 cm and the slant height is 25 cm. Find the volume and the curved surface of the cone.
Solution: Given perimeter of the base of a cone = 44 cm 2r = 44 2×22/7×r = 44 r = 44×7/(2×22) r = 7 cm Slant height, l = 25 height, h = √(l2-r2) h = √(252-72) h = √(625-49) h = √576 h = 24 cm Volume...
The perimeter of the base of a cone is 44 cm and the slant height is 25 cm. Find the volume and the curved surface of the cone.
Solution: Given perimeter of the base of a cone = 44 cm 2r = 44 2×22/7×r = 44 r = 44×7/(2×22) r = 7 cm Slant height, l = 25 height, h = √(l2-r2) h = √(252-72) h = √(625-49) h = √576 h = 24 cm Volume...
Find what length of canvas 2 m in width is required to make a conical tent 20 m in diameter and 42 m in slant height allowing 10% for folds and the stitching. Also find the cost of the canvas at the rate of Rs 80 per metre.
Solution: Given diameter of the conical tent, d = 20 m radius, r = d/2 = 20/2 = 10 m Slant height, l = 42 m Curved surface area of the conical tent = rl = (22/7)×10×42 = 22×10×6 = 1320 m2 So the...
(a) The ratio of the base radii of two right circular cones of the same height is 3 : 4. Find the ratio of their volumes.
(b) The ratio of the heights of two right circular cones is 5 : 2 and that of their base radii is 2 : 5. Find the ratio of their volumes.
(c) The height and the radius of the base of a right circular cone is half the corresponding height and radius of another bigger cone. Find: (i) the ratio of their volumes.
(ii) the ratio of their lateral surface areas.
Solution: (a) Let r1 and r2 be the radius of the given cones and h be their height. Ratio of radii, r1:r2 = 3:4 Volume of cone, V1 = (1/3)r12h Volume of cone, V2 = (1/3)r22h V1 /V1 = (1/3)r12h/...
A Jocker’s cap is in the form of a right circular cone of base radius 7 cm and height 24 cm. Find the area of the cloth required to make 10 such caps.
Solution: Given height of the cone, h = 24 cm Radius, r = 7 cm We know that l2 = h2+r2 l2 = 242+72 l2 = 576+49 l2 = 625 l = √625 l = 25 Curved surface area = rl = (22/7)×7×25 = 22×25 = 550 cm2 So...
The slant height and base diameter of a conical tomb are 25 m and 14 m respectively. Find the cost of white washing its curved surface area at the rate of Rs 210 per 100 m2.
Solution: Given slant height of conical tomb, l = 25 m Base diameter, d = 14 m So radius, r = 14/2 = 7 m Curved surface area = rl = (22/7)×7×25 = 550 m2 Hence the curved surface area of the cone is...
The height of a cone is 15 cm. If its volume is 1570 cm2 , find the radius of the base. (Use π = 3.14)
Solution: Given height of a cone, h = 15 cm Volume of the cone = 1570 cm3 (1/3)r2h = 1570 (1/3)3.14 ×r2×15 = 1570 5 ×3.14×r2 = 1570 r2 = 1570/5×3.14 = 314/3.14 = 100 r = 10 Hence the radius of the...
A conical pit of top diameter 3.5 m is 12 m deep. What is its capacity in kiloliters ?
Solution: Given diameter, d = 3.5 m So radius, r = 3.5/2 = 1.75 Depth, h = 12 m Volume of the cone = (1/3)r2h =(1/3)×(22/7)×1.752×12 = (22/7)× 1.752×4 = 38.5 m3 = 38.5 kilolitres [1 kilolitre = 1m3]...
Find the capacity in litres of a conical vessel with
(i) radius 7 cm, slant height 25 cm
(ii) height 12 cm, slant height 13 cm
Solution: Given radius, r = 7 cm Slant height, l = 25 cm We know that l2 = h2+r2 Height of the conical vessel, h = √(l2-r2) = √(252-72) = √(625-49) = √576 = 24 cm Volume of the cone = (1/3)r2h...
Find the volume of the right circular cone with
(i) radius 6 cm and height 7 cm
(ii) radius 3.5 cm and height 12 cm.
Solution: (i)Given radius, r = 6 cm Height, h = 7 cm Volume of the cone = (1/3)r2h =(1/3)×(22/7)×62×7 = 22×12 = 264 cm3 Hence the volume of the cone is 264 cm3. (ii) Given radius, r = 3.5 cm Height,...
Curved surface area of a cone is 308 cm2 and its slant height is 14 cm. Find , (i)radius of the base (ii)total surface area of the cone.
Solution: (i) Given curved surface area of the cone = 308 cm2 Slant height of the cone, l = 14 cm rl = 308 (22/7)×r×14 = 308 r = 308×7/(22×14) = 7 Hence the radius of the cone is 7 cm. (ii)Total...
Diameter of the base of a cone is 10.5 cm and slant height is 10 cm. Find its curved surface area.
Solution: Given diameter of the cone = 10.5 cm Radius, r = d/2 = 10.5/2 = 5.25 cm Slant height of the cone, l = 10 cm Curved surface area of the cone = rl = (22/7)×5.25×10 = 165 cm2 Hence the curved...
Write whether the following statements are true or false. Justify your answer.
(i) If the radius of a right circular cone is halved and its height is doubled, the volume will remain unchanged.
(ii) A cylinder and a right circular cone are having the same base radius and same height. The volume of the cylinder is three times the volume of the cone.
(iii) In a right circular cone, height, radius and slant height are always the sides of a right triangle.
Solution: (i)Volume of cone = (1/3)r2h If radius is halved and height is doubled, then volume = (1/3)(r/2)2 2h = (1/3)r2h/2 If the radius of a right circular cone is halved and its height is...
A soft drink is available in two packs
(i) a tin can with a rectangular base of length 5 cm and width 4 cm, having a height of 15 cm
(ii) a plastic cylinder with circular base of diameter 7 cm and height 10 cm. Which container has greater capacity and by how much?
Solution: (i) Length of the can, l = 5 cm Width, b = 4 cm Height, h = 15 cm Volume of the can = lbh = 5×4×15 = 300 cm3 (ii) Diameter of the cylinder, d = 7 cm Radius, r = d/2 = 7/2 = 3.5 cm Height,...
A lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled in the interior. The diameter of the pencil is 7 mm and the diameter of the graphite is 1 mm. If the length of the pencil is 14 cm, find the volume of the wood and that of the graphite.
Solution: Given length of the pencil, h = 14 cm Diameter of the pencil = 7 mm radius, R = 7/2 mm = 7/20 cm Diameter of the graphite = 1 mm Radius of graphite, r = ½ mm = 1/20cm Volume of graphite =...
The given figure shows a metal pipe 77 cm long. The inner diameter of a cross-section is 4 cm and the outer one is 4.4 cm. Find its
(i) inner curved surface area
(ii) outer curved surface area
(iii) total surface area.
Solution: Given height of the metal pipe = 77 cm Inner diameter = 4 cm Inner radius, r = d/2 = 4/2 = 2 cm Outer diameter = 4.4 cm Outer radius, R = d/2 = 4.4/2 = 2.2 cm (i)Inner curved surface area...
A cylindrical tube open at both ends is made of metal. The internal diameter of the tube is 11.2 cm and its length is 21 cm. The metal thickness is 0.4 cm. Calculate the volume of the metal.
Solution: Given internal diameter of the tube = 11.2 cm Internal radius, r = d/2 = 11.2/2 = 5.6 cm Length of the tube, h = 21 cm Thickness = 0.4 cm Outer radius, R= 5.6+0.4 = 6 cm Volume of the...
Two cylindrical jars contain the same amount of milk. If their diameters are in the ratio 3 : 4, find the ratio of their heights.
Solution: Let r1 and r2 be the radius of the two cylinders and h1 and h2 be their heights. Given ratio of the diameter = 3:4 Then the ratio of radius r1:r2 = 3:4 Given volume of both jars are same....
The ratio between the curved surface and the total surface of a cylinder is 1 : 2. Find the volume of the cylinder, given that its total surface area is 616 cm2.
Solution: Given the ratio of curved surface area and the total surface area = 1:2 Total surface area = 616 cm2 Curved surface area = 616/2 = 308 cm2 2rh = 308 rh = 308/2 = 308×7/2×22 rh = 49 …(i)...
(i) The sum of the radius and the height of a cylinder is 37 cm and the total surface area of the cylinder is 1628 cm2 . Find the height and the volume of the cylinder.
(ii) The total surface area of a cylinder is 352 cm2 . If its height is 10 cm, then find the diameter of the base.
Solution: (i) Let r be the radius and h be the height of the cylinder. Given the sum of radius and height of the cylinder, r+h = 37 cm Total surface area of the cylinder = 1628 cm2 2r(r+h) = 1628...
The radius of the base of a right circular cylinder is halved and the height is doubled. What is the ratio of the volume of the new cylinder to that of the original cylinder?
Solution: Let the radius of the base of a right circular cylinder be r and height be h. Volume of the cylinder, V1 = r2h The radius of the base of a right circular cylinder is halved and the height...
Find the ratio between the total surface area of a cylinder to its curved surface area given that its height and radius are 7.5 cm and 3.5 cm.
Solution: Given radius of the cylinder, r = 3.5 cm Height of the cylinder, h = 7.5 cm Total surface area = 2r(r+h) Curved surface area = 2rh Ratio of Total surface area to curved surface area =...
The barrel of a fountain pen, cylindrical in shape, is 7 cm long and 5 mm in diameter. A full barrel of ink in the pen will be used up when writing 310 words on an average. How many words would use up a bottle of ink containing one-fifth of a litre?
Answer correct to the nearest. 100 words. Solution: Height of the barrel of a pen, h = 7 cm Diameter, d = 5mm = 0.5 cm Radius, r = d/2 = 0.5/2 = 0.25 cm Volume of the barrel of pen, V = r2h =...
A cylinder has a diameter of 20 cm. The area of curved surface is 1000 cm2. Find (i) the height of the cylinder correct to one decimal place. (ii) the volume of the cylinder correct to one decimal place. (Take π = 3.14)
Solution: (i) Given diameter of the cylinder, d = 20 cm Radius, r = d/2 = 20/2 = 10 cm Curved surface area = 1000 cm2 2rh = 1000 2×3.14×10×h = 1000 62.8h = 1000 h = 1000/62.8 = 15.9 cm Hence the...
The area of the curved surface of a cylinder is 4400 cm2, and the circumference of its base is 110 cm. Find
(i) the height of the cylinder.
(ii) the volume of the cylinder.
Solution: Given curved surface area of a cylinder = 4400 cm2 Circumference of its base = 110 cm 2r = 110 r = 110/2 = (110×7)/2×22 = 17.5 cm (i) Curved surface area of a cylinder, 2rh = 4400...
A wooden pole is 7 m high and 20 cm in diameter. Find its weight if the wood weighs 225 kg per m3.
Solution: Given height of the pole, h = 7 m Diameter of the pole, d = 20 cm radius, r = d/2 = 20/2 = 10 cm = 0.1m Volume of the pole = r2h = (22/7)×0.12×7 = 0.22 m3 Weight of wood per m3 = 225 kg...
If the volume of a cylinder of height 7 cm is 448 π cm3, find its lateral surface area and total surface area.
Solution: Given Height of the cylinder, h = 7 cm Volume of the cylinder, V = 448 cm3 r2h = 448 ×r2×7 = 448 r2 = 448/7 = 64 r = 8 Lateral surface area = 2rh = 2××8×7 = 112 cm2 Total surface area =...
A road roller (in the shape of a cylinder) has a diameter 0.7 m and its width is 1.2 m. Find the least number of revolutions that the roller must make in order to level a playground of size 120 m by 44 m.
Solution: Given diameter of the road roller, d = 0.7 m Radius, r = d/2 = 0.7/2 = 0.35 m Width, h = 1.2 m Curved surface area of the road roller = 2rh =2 ×(22/7)×0.35×1.2 = 2.64 m2 Area of the play...
(i) How many cubic metres of soil must be dug out to make a well 20 metres deep and 2 metres in diameter?
(ii) If the inner curved surface of the well in part (i) above is to be plastered at the rate of Rs 50 per m2, find the cost of plastering.
Solution: (i) Given diameter of the well, d = 2 m Radius, r = d/2 = 2/2 = 1 m Depth of the well, h = 20 m Volume of the well, V = r2h = (22/7)×12×20 = 62.85 m3 Hence the amount of soil dug out to...
In the given figure, a rectangular tin foil of size 22 cm by 16 cm is wrapped around to form a cylinder of height 16 cm. Find the volume of the cylinder.
Solution: Given height of the cylinder, h = 16 cm When rectangular foil of length 22 cm is folded to form cylinder, the base circumference of the cylinder is 22cm 2r = 22 r = 22/2 = 3.5 cm Volume of...
A school provides milk to the students daily in cylindrical glasses of diameter 7 cm. If the glass is filled with milk upto a height of 12 cm, find how many litres of milk is needed to serve 1600 students.
Solution: Given diameter of the cylindrical glass, d = 7 cm Radius, r = d/2 = 7/2 = 3.5 cm Height of the cylindrical glass, h = 12 cm Volume of the cylindrical glass, V = r2h = (22/7)×3.52×12 = 462...
An electric geyser is cylindrical in shape, having a diameter of 35 cm and height 1.2m. Neglecting the thickness of its walls, calculate
(i) its outer lateral surface area,
(ii) its capacity in litres.
Solution: Given diameter of the cylinder, d = 35 cm radius, r = d/2 = 35/2 = 17.5 cm Height of the cylinder, h = 1.2 m = 120 cm (i)Outer lateral surface area = 2rh = 2×(22/7)×17.5×120 = 13200 cm2...
Find the total surface area of a solid cylinder of radius 5 cm and height 10 cm. Leave your answer in terms of π.
Solution: Given radius of the cylinder, r = 5 cm Height of the cylinder, h = 10 cm Total surface area = 2r(r+h) = 2×5(5+10) = 2×5×15 = 150 cm2 Hence the total surface area of the solid cylinder is...