Surface Area of a Sphere, Hemi-Sphere and Spherical Shell

The front compound wall of a house is decorated by wooden spheres of diameter $21 \mathrm{cm}$ placed on small supports as shown in Fig. Eight such spheres are used for this purpose, and are to be painted silver. Each support is a cylinder of radius $1.5 \mathrm{cm}$ and height $7 \mathrm{cm}$ and is to be painted black. Find the cost of paint required if silver paint costs $25$ paise per ${\mathrm{cm}}^2$ and black paint costs $5$ paise per ${\mathrm{cm}}^2$.

A storage tank consists of a circular cylinder with a hemisphere adjoined on either end. If the external diameter of the cylinder be $1.4 \mathrm{m}$ and its length be $8 \mathrm{m}$, find the cost of painting it on the outside at the rate of $₹10 \mathrm{per} {\mathrm{m}}^2$.

The dome of a building is in the form of a hemisphere. Its radius is $63 \mathrm{dm}$. Find the cost of painting it at the rate of $₹ 2$ per $sq.m$.

A hemispherical bowl made of brass has inner diameter $10.5 \mathrm{cm}$. Find the cost of tin-plating it on the inside at the rate of $₹ 4$ per $100 {\mathrm{cm}}^2$.

A wooden toy is in the form of cone surrmounted on a hemisphere. The diameter of the base of the cone is $16 cm$ and its height is $15 \mathrm{cm}$. Find the cost of painting the toy at Rs.$7$ per $100 {\mathrm{cm}}^2$.

A hemi-spherical dome of a building needs to be painted. If the circumference of the base of the dome is $17.6 \mathrm{m}$, find the cost of painting it, given the cost of painting is $₹ 5$ per $100 {\mathrm{cm}}^2$.

The diameter of the moon is approximately one fourth of the diameter of the earth. Find the ratio of their surfcae areas.

If a solid sphere of radius $10 \mathrm{cm}$ is moulded into $8$ spherical solid balls of equal radius, then the surface area of each ball is $k\mathrm{\pi } {\mathrm{cm}}^2$, then find the value of $k$.

If the ratio of volumes of two spheres is $1:8$ then the ratio of their surface areas is

The ratio of the total surface area of a sphere and a hemisphere of same radius is

The total surface area of a hemisphere of radius $r$ is

A cylinder of same height and radius is placed on the top of a hemisphere. Find the curved surface area of the shape if the length of the shape be $7 \mathrm{cm}$. 

Assuming the earth to be a sphere of radius $6370 \mathrm{km}$, how many $\mathrm{square} \mathrm{kilometers}$ is area of the land, if three-fourth of the earth's surface is covered by water?

The surface area of a sphere is $5544 {\mathrm{cm}}^2$, find its diameter.( in $\mathrm{cm}$).

Find the total surface area of a hemisphere and a solid hemisphere each of radius $10$ $\mathrm{cm}$ ( Use $\mathrm{\pi }=3.14$).

 Find the surface area of a sphere of a diameter $3.5 \mathrm{cm}$( in ${\mathrm{cm}}^2$).
 

Find the surface area of a sphere of a diameter $21 \mathrm{cm}$.( in ${\mathrm{cm}}^2$).
 

Find the surface area of a sphere of diameter $14 \mathrm{cm}$.( in ${\mathrm{cm}}^2$).
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 Find the surface area of a sphere of whose radius is $14 \mathrm{cm}$.(in ${\mathrm{cm}}^2$).
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Find the surface area of a sphere of radius whose $10.5 \mathrm{cm}$.(in ${\mathrm{cm}}^2$)
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