Q. 15.0( 1 Vote )

Find the surface area of spheres of the following radii.

(1)

(2)

(3)

(4)

(5)

(6)

Answer :

(1). When given is radius of the sphere, r = 7 cm.

We have



Surface area of sphere is given by


Surface area = 4 πr2


Substituting the given value in the above equation, we get


Surface area = 4 × 22/7 × 72


Surface area = (4 × 22 × 7 × 7)/7


Surface area = 616


Thus, surface area is 616 cm2.


(2). When given is radius of the sphere, r = 10.5 cm.


We have



Surface area of sphere is given by


Surface area = 4 πr2


Substituting the given value in the above equation, we get


Surface area = 4 × 22/7 × (10.5)2


Surface area = (4 × 22 × 10.5 × 10.5)/7


Surface area = 9702/7 = 1386


Thus, surface area is 1386 cm2.


(3). When given is radius of the sphere, r = 10 cm.


We have



Surface area of sphere is given by


Surface area = 4 πr2


Substituting the given value in the above equation, we get


Surface area = 4 × 3.14 × (10)2


Surface area = 4 × 3.14 × 100


Surface area = 1256


Thus, surface area is 1256 cm2.


(4). When given is radius of the sphere, r = 2.8 cm.


We have



Surface area of sphere is given by


Surface area = 4 πr2


Substituting the given value in the above equation, we get


Surface area = 4 × 22/7 × (2.8)2


Surface area = (4 × 22 × 2.8 × 2.8)/7


Surface area = 689.92/7 = 98.56


Thus, surface area is 98.56 cm2.


(5). When given is radius of the sphere, r = 9.8 m.


We have



Surface area of sphere is given by


Surface area = 4 πr2


Substituting the given value in the above equation, we get


Surface area = 4 × 22/7 × (9.8)2


Surface area = (4 × 22 × 9.8 × 9.8)/7


Surface area = 8451.52/7 = 1207.36


Thus, surface area is 1207.36 m2.


(6). When given is radius of the sphere, r = 42 m.


We have



Surface area of sphere is given by


Surface area = 4 πr2


Substituting the given value in the above equation, we get


Surface area = 4 × 22/7 × (42)2


Surface area = (4 × 22 × 42 × 42)/7


Surface area = 155232/7 = 22176


Thus, surface area is 22176 m2.


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