Question

The Surface area of a sphere is 394.
24 cm square. If its radius is decreased by
25%, what will be the decrease in
Surface area?​

Answer 1

✰✰ANSWER✰✰

we know that, the surface area of square is 4πr²

Give surface area is =394.24cm²

so,

➪4πr²=394.24

➪ 4×(22/7) ×r²=394.25

➪r²=(394.24×7/88)

➪ r²=31.36

square-root of both sides,

➪ r=5.6cm

now give that, radius is decrease by 25%

so,

➪new radius=(5.6×75)/100=4.2cm

now

➪new surface area=4×(22/7)×(4.2)²=88×0.6×4.2=221.76cm

so

➪ decrease in surface area=394.25-221.76

= 172.48.

➪ hence the decrease in surface area is 172.48cm²