If the diameter of a sphere is decreased by 25%, its curved surface area will be decreased by ;

Percentage decrease $=left(-2 x+frac{x^{2}}{100} ight) \%$ $=(-50+6.25) \%=-43.75 \%$ Alternative: Fraction of $25 \%=frac{25}{100}=frac{1}{4}$ ( 4 – 1 = 3 Diameter of sphare is reducing)

Curved surface area $left(left(frac{d}{2} ight)^{2} ight) ightarrowleft(frac{4}{2} ight)^{2} quadleft(frac{3}{2} ight)^{2}$

16 : 9

Percent reduction $=frac{16-9}{16} imes 100=43.75 \%$