Question

the diameter of sphere is decreased by 20% by what percent does it curved surface area decrease or increase​

Answer 1

it will increase by 32 percent

Answer 2

Answer:

Decreased by 32%

Step-by-step explanation:

Original diameter d.

New diameter = 0.8d  ( removed 20% of d; i.e. removed 0.2d)

Original SA = 4 π r² = 4 π ( d/2 )² = π d²

New SA = π ( new diameter )² = π × 0.8² × d² = π × 0.64 × d²

As a proportion of the original SA, the new SA is:

New SA / Original SA = ( π × 0.64 × d² ) / ( π d² ) = 0.64

So new SA is 64% of original SA.

That is is decreased by (100-64)% = 32%.