Question

A solid sphere of diameter 7 cm is cut into two equal halves. what will be the increase (in cm2) in the total surface area ?

Answer 1

Here we will need to find the area of the sphere and subtract it from the area of the 2- half spheres

1) Area of sphere: 

Surface area of sphere is given by the following formula:

4 π r ²    

=  4 × 22/7 × 7² 

 = 4 × 22 × 7

= 616 cm²

2) Area of the 2 - half spheres

Surface area of half a sphere is given by: 

(4πr²/2 + πr²)

(616/2  + 22/7 × 7²)2

(308 + 154)2

462 × 2 = 924cm²

Area of the 2-half spheres = 924cm²

Therefore the increase in surface area = 

Area of the 2-half spheres - area of the whole sphere

924 cm² - 616 cm²

= 308cm²