Question

Formula surface area of sphere of diameter. 21 cm

Answer 1

Surface area of sphere = 4πr²

If diameter = 21 cm

Then radius = 21/2


=> Surface area = 4π(21/2)²

=> Surface area = 4π ×21²/4

=> Surface area = 21² × π

=> Surface area = 441 × 22/7

=> Surface area = 63 × 22

=> Surface area = 1386 cm²



Formula for surface area

= 4πr²
or,

πd²

Answer 2

Hola!

Here's your answer -

Surface area of Sphere = 4πr²

Diameter = 21cm

So, Radius = 21/2 cm

Lets take π = 22/7

= 4 × 22/7 × (21/2)²

= 4 × 22/7 × 441 × 4

Number 4 will be cut

Therefore,

22/7 × 441

= 63 × 22

= 1386 cm²


Hope it helps!