Advertisements
Advertisements
Question
Find the surface area of a sphere of diameter 21 cm.
Advertisements
Solution
Diameter = 21cm
Radius = `"diameter "/ 2 - 21/2 - 10.5cm`
∴ Surface area - `4πr^2 - 4π × (10.5)^2 - 4 × 22/7 × 10.5^2 - 1386 cm^2`
RELATED QUESTIONS
The radius of a spherical balloon increases from 7 cm to 14 cm as air is being pumped into it. Find the ratio of surface areas of the balloon in the two cases.
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.
Find the surface area of a sphere of radius 5.6 cm.
The surface area of a sphere is 5544 `cm^2`, find its diameter.
Assuming the earth to be a sphere of radius 6370 km, how many square kilo metres is area
of the land, if three-fourth of the earth’s surface is covered by water?
A hemi-spherical dome of a building needs to be painted. If the circumference of the base of
the dome is 17.6 cm, find the cost of painting it, given the cost of painting is Rs. 5 per l00
`cm^2`
The surface area of a sphere is 2464 cm2, find its volume.
The surface area of a solid sphere is increased by 12% without changing its shape. Find the percentage increase in its:
- radius
- volume
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.
A hemi-spherical bowl has negligible thickness and the length of its circumference is 198 cm. Find the capacity of the bowl.
Find the maximum volume of a cone that can be carved out of a solid hemisphere of radius r cm.
Determine the ratio of the volume of a cube to that of a sphere which will exactly fit inside the cube.
If a hollow sphere of internal and external diameters 4 cm and 8 cm respectively melted into a cone of base diameter 8 cm, then find the height of the cone.
Mark the correct alternative in each of the following:
In a sphere the number of faces is
The ratio of the total surface area of a sphere and a hemisphere of same radius is
If a solid sphere of radius r is melted and cast into the shape of a solid cone of height r, then the radius of the base of the cone is
A sphere is placed inside a right circular cylinder so as to touch the top, base and lateral surface of the cylinder. If the radius of the sphere is r, then the volume of the cylinder is
The ratio between the volume of a sphere and volume of a circumscribing right circular cylinder is
Find the surface area of a sphere, if its volume is 38808 cubic cm. `(π = 22/7)`
Find the volume of a sphere, if its surface area is 154 sq.cm.
Find the volume of the hollow sphere whose inner diameter is 8 cm and the thickness of the material of which it is made is 1 cm .
A hemispherical 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?
A solid, consisting of a right circular cone standing on a hemisphere, is placed upright, in a right circular cylinder, full of water and touches the bottom. Find the volume of water left in the cylinder, having given that the radius of the cylinder is 3 cm and its height is 6 cm; the radius of the hemisphere is 2 cm and the height of the cone is 4 cm. Give your answer to the nearest cubic centimetre.
A conical tent is to accommodate 77 persons. Each person must have 16 m3 of air to breathe. Given the radius of the tent as 7 m, find the height of the tent and also its curved surface area.
There is surface area and volume of a sphere equal, find the radius of sphere.
There is a ratio 1: 4 between the surface area of two spheres, find the ratio between their radius.
A sphere cut out from a side of 7 cm cubes. Find the volume of this sphere?
A vessel is in he form of an inverted cone. Its height is 11 cm., and the radius of its top which is open is 2.5 cm. It is filled with water up to the rim. When lead shots, each of which is a sphere of radius 0.25 cm., are dropped 2 into the vessel, `2/5`th of the water flows out. Find the number of lead shots dropped into the vessel.
A solid sphere is cut into two identical hemispheres.
Statement 1: The total volume of two hemispheres is equal to the volume of the original sphere.
Statement 2: The total surface area of two hemispheres together is equal to the surface area of the original sphere.
Which of the following is valid?
