Math question class 8

Q1) Find the surface area of sphere whose diameter is

a) 20 cm

b) 30 cm

c) 45 m

Ans a) 

      

Surface area of sphere= 4πr²

As diameter is 20 cm hence radius will be 10 cm ( r=d/2)

Therefore

Area = 4×22/7*10*10

          = 4×3.1428*100

          = 12.5714*100

          = 1257.14 cm²

Ans b)

Surface area of sphere= 4πr²

As diameter is 30 cm hence radius will be  15 cm ( r=d/2)

Therefore

Area = 4×22/7*15*15

          = 4×3.1428*

          = 12.5714*225

          = 2828.52 cm²

Ans c)

Surface area of sphere= 4πr²

As diameter is 45m hence radius will be 22.5 m ( r=d/2)

Therefore

Area = 4×22/7*22.5*22.5

          = 4×3.1428*506.25

          = 12.5714*506.25

          = 6364.17m²