Question

Diameter of sphere is decreased by 25% . By what percent its curved surface srea decrease

Answer 1

Answer:

56.25%

Step-by-step explanation:

Suppose the orginal radius is r and the new radius is R.

New diameter = old diameter increased by 25%

=> 2R = 2r + ( 25% of 2r )  = 2r + 0.25×2r = 1.25×2r

=> R = 1.25 r

New surface area / old surface area

= ( 4 π R² ) / ( 4 π r² )

= R² / r²  =  ( R / r )²  =  1.25²  =  1.5625 = 100% + 56.25%

=> New surface area = old surface area increased by 56.25%