Q. 15.0( 1 Vote )

# Find the surface area of spheres of the following radii.(1) (2) (3) (4) (5) (6)

(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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