A solid is in the form of a cylinder with hemispherical ends. The total height of the solid is 20 cm and the diameter of the cylinder is 7 cm. Find the total volume of the solid. (Use π=722)
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Answer:64081 cm3 ≈ 680.17 cm3
Radius r=3.5 cm. Height of the cylindrical part h=20−2×3.5=13 cm.
A right circular cylinder and a right circular cone have equal bases and equal heights. If their curved surface areas are in the ratio 8 : 5, then find the ratio between the radius of their bases to their height.
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Answer: 3 : 4
Let the common radius be r and height h; slant height of the cone l=r2+h2.
To protect plants from heat, a shed of iron rods covered with green cloth is made. The lower part of the shed is a cuboid mounted by semi-cylinder as shown in the figure. Find the area of the cloth required to make this shed, if dimensions of the cuboid are 14 m × 25 m × 16 m
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Answer: 1952 m2
Cloth covers the four walls of the cuboid, the curved surface of the semi-cylinder and its two semicircular ends (not the floor).
Radius of semi-cylinder =7 m, length =25 m.
Four walls =2(14+25)×16=1248 m2
Curved surface of semi-cylinder =πrl=722×7×25=550 m2
The internal and external radii of a hollow hemisphere are 52 cm and 10 cm respectively. A cone of height 57 cm and radius 52 cm is surmounted on the hemisphere as shown in the figure. Find the total surface area of the object in terms of π. (Use 2=1.4)
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Answer:355π cm2
Outer curved surface of hemisphere =2πR2=2π×100=200π
Ring at the rim =π(R2−r2)=π(100−50)=50π
Slant height of cone l=(52)2+(57)2=50+175=15 cm
Curved surface of cone =πrl=π×52×15=752π=75×1.4π=105π
The cone closes the hollow, so the inner surface is not exposed.
From each end of a solid cylinder of height 20 cm and base radius 7 cm, a cone of base radius 2.1 cm and height 5 cm is scooped out. Find the volume of the remaining solid.
A room is in the form of a cylinder surmounted by a hemispherical dome. The base radius of the hemisphere is half of the height of the cylindrical part. If the room contains 211408 m3 of air, find the height of the cylindrical part. (Use π=722).
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Answer:4 m
Let the radius be r; then the height of the cylinder is h=2r.
A solid is in the form of a cylinder with hemi–spherical ends of same radii. The total height of the solid is 20 cm and the diameter of the cylinder is 14 cm. Find the surface area of the solid.
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Answer: 880 cm2
Radius r=7 cm; height of the cylindrical part h=20−2×7=6 cm.
A juice glass is cylindrical in shape with hemi–spherical raised up portion at the bottom. The inner diameter of glass is 10 cm and its height is 14 cm. Find the capacity of the glass. (use π=3.14)
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Answer: 837.33 cm3 (approx.)
Radius r=5 cm, height h=14 cm.
Capacity = volume of cylinder − volume of hemisphere =πr2h−32πr3.
A vessel is in the form of a hollow hemisphere surmounted 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.
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Answer: 572 cm2
Radius r=7 cm; height of cylinder h=13−7=6 cm.
Inner surface area = CSA of hemisphere + CSA of cylinder =2πr2+2πrh.
A solid toy is in the form of a hemisphere surmounted by a right circular cone. The height of the cone is 2 cm and the diameter of the base is 4 cm. Determine the volume of the toy.
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Answer:8π=7176 cm3 (about 25.14 cm3)
Radius r=2 cm, height of cone h=2 cm.
Volume = volume of cone + volume of hemisphere =31πr2h+32πr3.
The difference between the outer and inner radii of a hollow right circular cylinder of length 14 cm is 1 cm. If the volume of the metal used in making the cylinder is 176 cm3, find the outer and inner radii of the cylinder.
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Answer: Outer radius = 2.5 cm, inner radius = 1.5 cm
Let outer radius be R and inner radius r; R−r=1.
Volume of metal =π(R2−r2)h=722(R2−r2)(14)=44(R2−r2)=176.
A wooden toy is made by scooping out a hemisphere of same radius as of cylinder, from each end of a wooden solid cylinder. If the height of the cylinder is 20 cm and its base is of radius 7 cm, find the total surface area of the toy.
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Answer: 1496 cm2
Total surface area = curved surface of cylinder + inner surfaces of the two hemispherical hollows.
The inner and outer radii of a hollow cylinder surmounted on a hollow hemisphere of same radii are 3 cm and 4 cm respectively. If height of the cylinder is 14 cm, then find its total surface area (inner and outer).
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Answer:253π=75566≈795.14cm2
Inner radius r=3 cm, outer radius R=4 cm, height of cylinder h=14 cm.
Outer surface: cylinder 2πRh=112π, hemisphere 2πR2=32π; total 144π.
Inner surface: cylinder 2πrh=84π, hemisphere 2πr2=18π; total 102π.
Ring at the open top: π(R2−r2)=7π.
Total surface area =144π+102π+7π=253π=253×722=75566≈795.14cm2.
A room is in the form of cylinder surmounted by a hemi-spherical dome. The base radius of hemisphere is one-half the height of cylindrical part. Find total height of the room if it contains (211408) m3 of air. (Take π=722)
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Answer: 6 m
Let the radius be r; height of cylinder h = 2r.
Volume =πr2(2r)+32πr3=38πr3.
38×722×r3=211408, so 21176r3=211408, r3=8, r = 2 m.
An empty cone is of radius 3 cm and height 12 cm. Ice-cream is filled in it so that lower part of the cone which is (61)th of the volume of the cone is unfilled but hemisphere is formed on the top. Find volume of the ice-cream. (Take π=3.14)
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Answer: 150.72 cm3
Volume of cone =31πr2h=31×3.14×9×12=113.04 cm3.
Filled part of cone =65×113.04=94.2 cm3.
Volume of hemisphere =32πr3=32×3.14×27=56.52 cm3.