Diameter of cylindrical tank = 2.8 m radius = 1.4 m Height = 4.2 m \[\begin{array}{*{35}{l}} Volume\text{ }of\text{ }water\text{ }filled\text{ }in\text{ }it\text{ }=\text{ }\pi {{r}^{2}}h \\...

### The cross-section of a tunnel is a square of side 7 m surmounted by a semicircle as shown in the following figure.The tunnel is 80 m long. Calculate:(iii) its floor area

FIGURE: Side of square (a) = 7m the radius of semi-circle = 7/2 m Length of the tunnel = 80 m \[\begin{array}{*{35}{l}} Area\text{ }of\text{ }cross\text{ }section\text{ }of\text{ }the\text{...

### The cross-section of a tunnel is a square of side 7 m surmounted by a semicircle as shown in the following figure.The tunnel is 80 m long. Calculate: (i) its volume (ii) the surface area of the tunnel (excluding the floor)

FIGURE: Side of square (a) = 7m the radius of semi-circle = 7/2 m Length of the tunnel = 80 m \[\begin{array}{*{35}{l}} Area\text{ }of\text{ }cross\text{ }section\text{ }of\text{ }the\text{...

### In the following diagram a rectangular platform with a semicircular end on one side is 22 meters long from one end to the other end. If the length of the half circumference is 11 meters, find the cost of constructing the platform, 1.5 meters high at the rate of Rs 4 per cubic meters.

Length of the platform = 22 m Circumference of semi-circle (c) = 11 m \[\begin{array}{*{35}{l}} radius\text{ }=\text{ }\left( c\text{ x }2 \right)/\text{ }\left( 2\text{ x }\pi \right)\text{...

### An iron pole consisting of a cylindrical portion 110 cm high and of base diameter 12 cm is surmounted by a cone 9 cm high. Find the mass of the pole, given that 1 cm3 of iron has 8 gm of mass (approx). (Take π = 355/113)

Radius of the base of poles (r) = 6 cm Height of the cylindrical part (h1) = 110 cm Height of the conical part (h2) = 9 cm \[\begin{array}{*{35}{l}} Total\text{ }volume\text{ }of\text{ }the\text{...

### Determine the ratio of the volume of a cube to that of a sphere which will exactly fit inside the cube.

Let edge of the cube = a Then, volume of the cube = a x a x a = a3 The sphere that exactly fits in the cube will have radius ‘a/2’ \[\begin{array}{*{35}{l}} Volume\text{ }of\text{ }sphere\text{...

### The diameter of a sphere is 6 cm. It is melted and drawn into a wire of diameter 0.2 cm. Find the length of wire.

Diameter of the sphere = 6 cm Radius = 3 cm \[~volume\text{ }=\text{ }4/3\text{ }\pi {{r}^{3~}}=\text{ }4/3\text{ x }22/7\text{ x }3\text{ x }3\text{ x }3\text{ }=\text{ }792/7\text{...

### A solid is in the form of a cone standing on a hemisphere with both their radii being equal to 8 cm and the height of cone is equal to its radius. Find in terms of π, the volume of the solid.

Radius of both cone and hemisphere = 8 cm And, height = 8 cm \[\begin{array}{*{35}{l}} Volume\text{ }of\text{ }the\text{ }solid\text{ }=\text{ }Volume\text{ }of\text{ }cone\text{ }+\text{...

### A right circular cylinder having diameter 12 cm and height 15 cm is full of ice-cream. The ice-cream is to be filled in identical cones of height 12 cm and diameter 6 cm having a hemi-spherical shape on the top. Find the number of cones required.

Diameter of the cylinder = 12 cm => radius = 6 cm Height of the cylinder = 15 cm Diameter of the cone = 6 cm =>radius = 3 cm Height of the cone = 12 cm Radius of the hemisphere = 3 cm Let the...

### A largest sphere is to be carved out of a right circular cylinder of radius 7 cm and height 14 cm. Find the volume of the sphere. (Answer correct to the nearest integer)

Radius of the largest sphere that can be formed inside the cylinder will be equal to the radius of the cylinder. radius of the largest sphere = 7 cm \[\begin{array}{*{35}{l}} Volume\text{ }of\text{...

### What is the least number of solid metallic spheres, each of 6 cm diameter, that should be melted and recast to form a solid metal cone whose height is 45 cm and diameter is 12 cm?

Diameter of solid metallic sphere = 6 cm So, its radius = 3 cm Height of solid metal cone = 45 Diameter of metal cone = 12 cm Its radius = 6 cm Let the number of solid metallic spheres be ‘n’...

### A wooden toy is in the shape of a cone mounted on a cylinder as shown alongside. If the height of the cone is 24 cm, the total height of the toy is 60 cm and the radius of the base of the cone = twice the radius of the base of the cylinder = 10 cm; find the total surface area of the toy. [Take π = 3.14]

Height of the cone (h) = 24 cm Height of the cylinder (H) = 36 cm Radius of the cone (r) = twice the radius of the cylinder = 10 cm Radius of the cylinder (R) = 5 cm \[\begin{array}{*{35}{l}}...

### A vessel is a hollow cylinder fitted with a hemispherical bottom of the same base. The depth of the cylindrical part is 4(2/3) m and the diameter of hemisphere is 3.5 m. Calculate the capacity and the internal surface area of the vessel.

Diameter of the base = 3.5 m So, its radius = 3.5/2 m = 1.75 m = 7/4 m Height of cylindrical part = 4 + 2/3 = 14/3 (i) \[\begin{array}{*{35}{l}} Capacity\text{ }\left( volume \right)\text{ }of\text{...

### A cylindrical boiler, 2 m high, is 3.5 m in diameter. It has a hemispherical lid. Find the volume of its interior, including the part covered by the lid.

Diameter of cylindrical boiler = 3.5 m So, the radius (r) = 3.5/2 = 35/20 = 7/4 m Height (h) = 2m Radius of hemisphere (R) = 7/4 m \[\begin{array}{*{35}{l}} Total\text{ }volume\text{ }of\text{...

### A circus tent is cylindrical to a height of 8 m surmounted by a conical part. If total height of the tent is 13 m and the diameter of its base is 24 m; calculate: (i) total surface area of the tent (ii) area of canvas, required to make this tent allowing 10% of the canvas used for folds and stitching.

Height of the cylindrical part = H = 8 m Height of the conical part = h = (13 – 8) m = 5 m Diameter = 24 m Its radius \[\begin{array}{*{35}{l}} =\text{ }24/2\text{ }=\text{ }12\text{ }m \\...

### A circus tent is cylindrical to a height of 4 m and conical above it. If its diameter is 105 m and its slant height is 80 m, calculate the total area of canvas required. Also, find the total cost of canvas used at Rs 15 per meter if the width is 1.5 m

Radius of the cylindrical part of the tent (r) =105/2 m Slant height (l) = 80 m the total curved surface area of the tent \[\begin{array}{*{35}{l}} =\text{ }2\pi r\text{ }h\text{ }+\text{ }\pi rl ...

### From a solid cylinder whose height is 16 cm and radius is 12 cm, a conical cavity of height 8 cm and of base radius 6 cm is hollowed out. Find the volume and total surface area of the remaining solid.

Radius of solid cylinder (R) = 12 cm And, Height (H) = 16 cm \[\begin{array}{*{35}{l}} Volume\text{ }=\text{ }\pi {{R}^{2~}}h\text{ }=\text{ }22/7\text{ }x\text{ }12\text{ }x\text{ }12\text{...

### From a solid right circular cylinder with height 10 cm and radius of the base 6 cm, a right circular cone of the same height and same base are removed. Find the volume of the remaining solid.

Height of the cylinder (h) = 10 cm And radius of the base (r) = 6 cm Volume of the cylinder = πr2 h Height of the cone = 10 cm Radius of the base of cone = 6 cm \[\begin{array}{*{35}{l}}...

### A vessel is in the form of an inverted cone. Its height is 8 cm and the radius of the top which is open is 5 cm. It is filled with water up to the rim. When lead shots, each of which is a sphere of radius 0.5 cm, are dropped into the vessel, one-fourth of the water flows out. Find the number of lead shots dropped in the vessel.

Height of cone = 8 cm Radius = 5 cm \[\begin{array}{*{35}{l}} Volume\text{ }=~1/3\text{ }\pi {{r}^{2~}}h \\ =\text{ }1/3\text{ x }22/7\text{ x }5\text{ x }5\text{ x }8\text{ }c{{m}^{3}} \\ =\text{...

### The cubical block of side 7 cm is surmounted by a hemisphere of the largest size. Find the surface area of the resulting solid.

Since, the diameter of the largest hemisphere that can be placed on a face of a cube of side 7 cm will be 7 cm. radius = r = 7/2 cm It’s curved surface area = 2 πr2 = 2 x 22/7 x 7/2 x 7/2 = 77...

### From a rectangular solid of metal 42 cm by 30 cm by 20 cm, a conical cavity of diameter 14 cm and depth 24 cm is drilled out. Find:(iii) the weight of the material drilled out if it weighs 7 gm per cm3.

\[\left( iii \right)\text{ }Weight\text{ }of\text{ }material\text{ }drilled\text{ }out\text{ }=\text{ }1232\text{ x }7g\text{ }=\text{ }8624g\text{ }=\text{ }8.624\text{ }kg\]

### From a rectangular solid of metal 42 cm by 30 cm by 20 cm, a conical cavity of diameter 14 cm and depth 24 cm is drilled out. Find: (i) the surface area of the remaining solid (ii)the volume of remaining solid

Dimensions of rectangular solid l = 42 cm, b = 30 cm and h = 20 cm Conical cavity’s diameter = 14 cm its radius = 7 cm Depth (height) = 24 cm (i) Total surface area of cuboid...

### A buoy is made in the form of a hemisphere surmounted by a right cone whose circular base coincides with the plane surface of the hemisphere. The radius of the base of the cone is 3.5 m and its volume is two-third of the hemisphere. Calculate the height of the cone and the surface area of the buoy, correct to two decimal places.

Radius of the hemisphere part (r) = 3.5 m = 7/2 m Volume of hemisphere \[\begin{array}{*{35}{l}} =\text{ }2/3\text{ }\pi {{r}^{3}} \\ =\text{ }2/3\text{ x }22/7\text{ x }7/2x\text{ }7/2\text{ x...

### A cone of height 15 cm and diameter 7 cm is mounted on a hemisphere of same diameter. Determine the volume of the solid thus formed.

Height of the cone = 15 cm Diameter of the cone = 7 cm its radius = 3.5 cm Radius of the hemisphere = 3.5 cm Volume of the solid = Volume of the cone + Volume of the hemisphere...

### A hemi-spherical bowl of internal radius 9 cm is full of liquid. This liquid is to be filled into conical shaped small containers each of diameter 3 cm and height 4 cm. How many containers are necessary to empty the bowl?

Radius of hemispherical bowl = 9 cm \[Volume\text{ }=\text{ }2/3\text{ }\pi {{r}^{3}}~=\text{ }2/3\text{ }\pi {{9}^{3}}~=\text{ }2/3\text{ }\pi \text{ }x\text{ }729\text{ }=\text{ }486\text{ }\pi...

### A solid rectangular block of metal 49 cm by 44 cm by 18 cm is melted and formed into a solid sphere. Calculate the radius of the sphere.

Volume of rectangular block \[=\text{ }49\text{ x }44\text{ x }18\text{ }c{{m}^{3}}~=\text{ }38808\text{ }c{{m}^{3}}~\ldots \ldots \text{ }\left( i \right)\] Let r be the radius of sphere....

### Total volume of three identical cones is the same as that of a bigger cone whose height is 9 cm and diameter 40 cm. Find the radius of the base of each smaller cone, if height of each is 108 cm.

Let the radius of the smaller cone be r cm Diameter of bigger cone = 40 cm the radius = 20 cm and height = 9 cm \[\begin{array}{*{35}{l}} Volume\text{ }of\text{ }larger\text{ }cone\text{ }=\text{...

### The radii of the internal and external surfaces of a metallic spherical shell are 3 cm and 5 cm respectively. It is melted and recast into a solid right circular cone of height 32 cm. find the diameter of the base of the cone.

Height of the solid right circular cone = 32 cm Internal radius metallic spherical shell = 3 cm External radius spherical shell = 5 cm the volume of the spherical shell \[\begin{array}{*{35}{l}}...

### A hollow sphere of internal and external diameters 4 cm and 8 cm respectively is melted into a cone of base diameter 8 cm. Find the height of the cone.

External diameter of the hollow sphere = 8 cm radius (R) = 4 cm Internal diameter of the hollow sphere = 4 cm radius (r) = 2 cm Then, the volume of metal used in hollow sphere = Also given, Diameter...

### A solid sphere of radius 15 cm is melted and recast into solid right circular cones of radius 2.5 cm and height 8 cm. Calculate the number of cones recast.

Radius of the sphere = R = 15 cm So, the volume of sphere melted \[=\text{ }4/3\text{ }\pi {{R}^{2}}~=\text{ }4/3\text{ x }\pi \text{ x }15\text{ x }15\text{ x }15\] Radius of each cone recasted = r...

### The volume of one sphere is 27 times that of another sphere. Calculate the ratio of their: (i) radii (ii) surface areas

The volume of first sphere = 27 x volume of second sphere Let the radius of the first sphere = r1 and, radius of second sphere = r2 (i) Then, according to the question we have...

### 8 metallic sphere; each of radius 2 mm, are melted and cast into a single sphere. Calculate the radius of the new sphere.

Radius of metallic sphere = 2mm = 1/5 cm \[\begin{array}{*{35}{l}} Volume\text{ }=\text{ }4/3\text{ }\pi {{r}^{3}}~=\text{ }4/3\text{ x }22/7\text{ x }1/5\text{ x }1/5\text{ x }1/5\text{ }=\text{...

### How many balls each of radius 1 cm can be made by melting a bigger ball whose diameter is 8 cm.

Diameter of bigger ball = 8 cm radius of bigger ball = 4 cm \[Volume\text{ }=\text{ }4/3\text{ }\pi {{r}^{3}}~=\text{ }4/3\text{ }\pi \text{ }{{4}^{3}}~=\text{ }265\pi /3\text{ }c{{m}^{3}}\] Radius...

### A spherical ball of lead has been melted and made into identical smaller balls with radius equal to half the radius of the original one. How many such balls can be made?

Let the radius of the spherical ball = r the volume = 4/3 πr3 And, the radius of smaller ball = r/2 Volume of smaller ball \[=\text{ }4/3\text{ }\pi {{\left( r/2 \right)}^{3}}~=\text{ }4/3\text{...

### The volume of a sphere is 38808 cm3; find its diameter and the surface area.

Volume of the sphere = 38808 cm3 Let the radius of the sphere \[\begin{array}{*{35}{l}} =\text{ }r \\ 4/3\text{ }\pi {{r}^{3}}~=\text{ }38808 \\ 4/3\text{ x }\left( 22/7 \right)\text{ x...

### The surface area of a sphere is 2464 cm2, find its volume.

Surface area of the sphere = 2464 cm2 Let the radius of the sphere be r. surface area of the sphere \[\begin{array}{*{35}{l}} =\text{ }4\pi {{r}^{2}} \\ 4\pi {{r}^{2}}~=\text{ }2464 \\ 4\text{ x...

### There are two cones. The curved surface area of one is twice that of the other. The slant height of the latter is twice that of the former. Find the ratio of their radii.

Let slant height of the first cone = l So, the slant height of the second cone = 2l Radius of the first cone = r1 And, the radius of the second cone = r2 Curved surface area of first cone = πr1l...

### The diameters of two cones are equal. If their slant heights are in the ratio 5:4, find the ratio of their curved surface areas.

Let radius of each cone = r Given that, ratio between their slant heights = 5: 4 Let slant height of the first cone = 5x And slant height of second cone = 4x So, curved surface area of the first...

### Two right circular cones x and y are made, x having three times the radius of y and y having half the volume of x. Calculate the ratio between the heights of x and y.

Let radius of cone y = r radius of cone x = 3r volume of cone y = V Then, volume of cone x = 2V Let h1 be the height of x and h2 be the height of y. \[\begin{array}{*{35}{l}} Volume\text{ }of\text{...

### The radius and height of a right circular cone are in the ratio 5:12 and its volume is 2512 cubic cm. Find the radius and slant height of the cone. (Take π = 3.14)

The ratio between radius and height = 5: 12 Volume of the right circular cone = 2512 cm3 Let its radius (r) = 5x, its height (h) = 12x and slant height = l \[\begin{array}{*{35}{l}}...

### The circumference of the base of a 12 m high conical tent is 66 m. Find the volume of the air contained in it.

Circumference of the base (c) = 66 m Height of the conical tent (h) = 12 m Radius \[=\text{ }c/2\pi \text{ }=\text{ }66/\text{ }2\pi \text{ }=\text{ }\left( 33\text{ x }7 \right)/22\text{ }=\text{...

### The curved surface area of a cone is 12320 cm2. If the radius of its base is 56 cm, find its height.

Curved surface area of the cone = 12320 cm2 Radius of the base = 56 cm Let the slant height be ‘l’ Curved surface area \[\begin{array}{*{35}{l}} =\text{ }\pi rl\text{ }=\text{ }12320\text{...

### Find the volume of a cone whose slant height is 17 cm and radius of base is 8 cm.

Slant height of the cone (l) = 17 cm Base radius (r) \[\begin{array}{*{35}{l}} =\text{ }8\text{ }cm \\ {{l}^{2}}~=\text{ }{{r}^{2}}~+\text{ }{{h}^{2}} \\ {{h}^{2}}~=\text{ }{{l}^{2}}~-\text{...

### Find the minimum length in cm and correct to nearest whole number of the thin metal sheet required to make a hollow and closed cylindrical box of diameter 20 cm and height 35 cm. Given that the width of the metal sheet is 1 m. Also, find the cost of the sheet at the rate of Rs. 56 per m. Find the area of metal sheet required, if 10% of it is wasted in cutting, overlapping, etc.

Height of the cylinder box = h = 35 cm Base radius of the cylinder box = r = 10 cm Width of metal sheet = 1m = 100 cm Area of metal sheet required = total surface area of the box Length x width =...

### The radius of a solid right circular cylinder decreases by 20% and its height increases by 10%. Find the percentage change in its: (i) volume (ii) curved surface area

Let the original dimensions of the solid right cylinder be radius (r) and height (h) in cm. Then its volume = πr2h cm3and curved surface area = 2πrh Now, after the changes the new dimensions are:...

### The radius of a solid right circular cylinder increases by 20% and its height decreases by 20%. Find the percentage change in its volume.

The radius of a solid right cylinder (r) = 100 cm let the height of a solid right circular cylinder (h) = 100 cm The volume (original) of a solid right circular cylinder \[\begin{array}{*{35}{l}}...

### The height and the radius of the base of a cylinder are in the ratio 3:1. If its volume is 1029π cm3; find its total surface area.

The ratio between height and radius of a cylinder = 3:1 Volume = 1029π cm3 …….(i) the radius of the base = r Then, it’s height will be = 3r Volume \[\begin{array}{*{35}{l}} =\text{ }\pi...

### Find the total surface area of an open pipe of length 50 cm, external diameter 20 cm and internal diameter 6 cm.

Length of the open pipe = 50 cm Its external diameter = 20 cm It’s external radius (R) = 10 cm Its internal diameter = 6 cm => It’s internal radius (r) = 3 cm Surface area of pipe open from both...

### A cylindrical container with internal radius of its base 10 cm, contains water up to a height of 7 cm. Find the area of wetted surface of the cylinder.

Internal radius of the cylindrical container = 10 cm = r Height of water = 7 cm = h So, the surface area of the wetted surface \[\begin{array}{*{35}{l}} =\text{ }2\pi rh\text{ }+\text{ }\pi...

### A cylindrical container with diameter of base 42 cm contains sufficient water to submerge a rectangular solid of iron with dimensions 22 cm x 14 cm x 10.5 cm. Find the rise in level of the water when the solid is submerged.

Diameter of cylindrical container = 42 cm it’s radius (r) = 21 cm Dimensions of rectangular solid = 22cm x 14cm x 10.5cm The volume of solid = 22 x 14 x 10.5 cm3 ….. (i) Let the height of water = h...

### A metal pipe has a bore (inner diameter) of 5 cm. The pipe is 5 mm thick all round. Find the weight, in kilogram, of 2 metres of the pipe if 1 cm3 of the metal weights 7.7 g.

Inner radius of the pipe = r = 5/2 = 2.5 cm External radius of the pipe = R = Inner radius of the pipe + Thickness of the pipe \[=\text{ }2.5\text{ }cm\text{ }+\text{ }0.5\text{ }cm\text{ }=\text{...

### A cylinder has a diameter of 20 cm. The area of curved surface is 100 sq cm. Find: (i) the height of the cylinder correct to one decimal place. (ii) the volume of the cylinder correct to one decimal place.

The diameter of the cylinder = 20 cm the radius (r) = 10 cm and the curved surface area = 100 cm2 Height = h cm (i) Curved surface area \[\begin{array}{*{35}{l}} =\text{ }2\pi rh \\ 2\pi rh\text{...

### What length of solid cylinder 2 cm in diameter must be taken to recast into a hollow cylinder of external diameter 20 cm, 0.25 cm thick and 15 cm long?

External diameter of hollow cylinder = 20 cm So, it’s radius = 10 cm = R Thickness = 0.25 cm the internal radius \[=\text{ }\left( 10\text{ }-\text{ }0.25 \right)\text{ }=\text{ }9.75\text{...

### How many cubic meters of earth must be dug out to make a well 28 m deep and 2.8 m in diameter? Also, find the cost of plastering its inner surface at Rs 4.50 per sq meter.

Radius of the well = 2.8/2 = 1.4 m Depth of the well = 28 m Hence, the volume of earth dug out \[\begin{array}{*{35}{l}} =~\pi {{r}^{2}}h \\ =\text{ }\left( 22/7 \right)\text{ x }1.4\text{ x...

### A cylinder of circumference 8 cm and length 21 cm rolls without sliding for 4½ seconds at the rate of 9 complete rounds per second. Find: (i) distance travelled by the cylinder in 4½ seconds, and (ii) the area covered by the cylinder in 4½ seconds

Base circumference of cylinder (c) = 8 cm So, the radius \[=\text{ }c/2\pi \text{ }=\text{ }\left( 8\text{ x }7 \right)/\text{ }\left( 2\text{ x }22 \right)\text{ }=\text{ }14/11\text{ }cm\] Length...

### The inner radius of a pipe is 2.1 cm. How much water can 12 m of this pipe hold?

The inner radius of the pipe = 2.1 cm Length of the pipe = 12 m = 1200 cm Volume of the pipe \[\begin{array}{*{35}{l}} =\text{ }\pi {{r}^{2}}h\text{ }=\text{ }22/7\text{ x }{{2.1}^{2}}~x\text{...

### The height of a circular cylinder is 20 cm and the radius of its base is 7 cm. Find: (i) the volume (ii) the total surface area.

Since, a circular cylinder whose Height, h = 20 cm and base radius, r = 7 cm (i) Volume of cylinder \[\begin{array}{*{35}{l}} =\text{ }\pi {{r}^{2}}h\text{ }=\text{ }22/7\text{ }x\text{...