Advertisements
Advertisements
प्रश्न
Find the surface area of a sphere of diameter 21 cm.
`["Assume "pi=22/7]`
Advertisements
उत्तर
Radius (r) of sphere = `"Diameter"/2`
= `(21/2) cm`
= 10.5 cm
Surface area of sphere = 4πr2
= `[4xx22/7xx(10.5)^2] cm^2`
= 1386 cm2
Therefore, the surface area of a sphere having diameter 21 cm is 1386 cm2.
APPEARS IN
संबंधित प्रश्न
The diameter of the moon is approximately one-fourth of the diameter of the earth. Find the ratio of their surface area.
A right circular cylinder just encloses a sphere of radius r (see figure). Find
- surface area of the sphere,
- curved surface area of the cylinder,
- ratio of the areas obtained in (i) and (ii).
The surface area of a solid metallic sphere is 2464 cm2. It is melted and recast into solid right circular cones of radius 3.5 cm and height 7 cm. Calculate:
- the radius of the sphere.
- the number of cones recast. (Take π = `22/7`)
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 hollow sphere of internal and external diameter 4 cm and 8 cm respectively is melted into a cone of base diameter 8 cm. Find the height of the cone.
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.
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.
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 the wire.
Determine the ratio of the volume of a cube to that of a sphere which will exactly fit inside the cube.
The hollow sphere, in which the circus motor cyclist performs his stunts, has a diameter of 7 m. Find the area available to the motorcyclist for riding.
The surface area of a sphere of radius 5 cm is five times the area of the curved surface of a cone of radius 4 cm. Find the height of the cone.
The total surface area of a hemisphere of radius r is
A sphere and a cube are of the same height. The ratio of their volumes is
If a sphere is inscribed in a cube, then the ratio of the volume of the sphere to the volume of the cube 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 cone, a hemisphere and a cylinder stand on equal bases and have the same height. The ratio of their volumes is
Find the surface area and volume of sphere of the following radius. (π = 3.14)
4 cm
Find the length of the wire of diameter 4 m that can be drawn from a solid sphere of radius 9 m.
Find the volume and surface area of a sphere of diameter 21 cm.
