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2015-03-05T23:05:39+05:30

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CSA of sphere =4πr² = πd²
if diameter is decreased by 25%,
new diameter = d - 0.25d = 0.75d 

final CSA = π(0.75d)² = 0.5625 πd²

decrease in CSA = πd² - 0.5625 πd² = 0.4375 πd²
%  decrease = (0.4375 πd² / πd² ) ×100 = 43.75%
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take πd² common
πd² - 0.5625 πd² = πd²(1-0.5625) =πd² * 0.4375 = 0.4375 πd²
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2015-03-06T05:14:08+05:30

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Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
let diameter be 2x
then radius will be x

older C.S.A.= 4πr²
                 =4πx²
when diameter is decreased by 25%
new diameter 2x - 2x * 25/100
                   2x - x/2
                   =3x/2
new radius = 3x / 2* 1/2
                 3x/4
new C.S.A.= 4π(3x/4)²
                 4π9x²/16
                =9πx²/4
increase n S.A. = 4πx²- 9πx²/4
                    =πx²(4-9/4)
                    =πx²7/4

                           7πx²  X 100                7 X 25
 % increaed  =     -----------------------  =   ------------------- =  43.75%
                             4πx² X 4                    4             






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