Question

The surface area of a sphere is 9856 sq cm.If its radius is decreased by 25% , what will be the decrease in the surface area?

Answer 1

$a1 \: = \pi \: r {}^{2}$

a2=

$\pi \: (r2) {}^{2}$

As radius is decresed by 25% so

$r2 = \frac{3}{4} r$

On dividing A1 & A2

$\frac{a1}{a2} = \frac{16}{9}$

Put a1 = 9856

we get a2= 9 x 616 = 5544

HERE IS THE ANSWER