Q.

If the surface area of a sphere is 616 cm², its diameter (in cm) is:

1 7  
2 14  
3 21  
4 56  

Ans.

(2)

4πr2=616⇒r2=616×14×722=49⇒r=7 cmDiameter = 2r = 2 × 7 = 14 cm