Surface area of a sphere of radius $r$ = 4 times area of circle.
= 4 $πr^2$
Curved surface area of a hemisphere = half the surface area of the sphere.
= 2 $πr^2$
Total Surface Area of a Hemisphere= curved surface area of a hemisphere + area of top circular portion
= 2 $πr^2$ + $πr^2$
= 3$πr^2$
Assume π = $22/7$ unless stated otherwise
1. Find the surface area of a sphere of radius: (i) 10.5 cm (ii) 5.6 cm (iii) 14 cm 2. Find the surface area of a sphere of diameter: (i) 14 cm (ii) 21 cm (iii) 3.5 m 3. Find the total surface area of a hemisphere of radius 10 cm. (Use π = 3.14) 4. 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. 5. A hemispherical bowl made of brass has inner diameter 10.5 cm. Find the cost of tin-plating it on the inside at the rate of ₹ 16 per 100 $cm^2$. 6. Find the radius of a sphere whose surface area is 154 $cm^2$. 7. The diameter of the moon is approximately one fourth of the diameter of the earth. Find the ratio of their surface areas. 8. A hemispherical bowl is made of steel, 0.25 cm thick. The inner radius of the bowl is 5 cm. Find the outer curved surface area of the bowl. 9. A right circular cylinder just encloses a sphere of radius r. Find (i) surface area of the sphere, (ii) curved surface area of the cylinder, (iii) ratio of the areas obtained in (i) and (ii).