According to the formula
Percentage increase in surface area = [ 2x + x²/100]%

Correct Option: A

According to the formula
Percentage increase in surface area = [ 2x + x²/100]%
= [2 x 3 + (3)²/100]%
= [6 + 0.09]%
= 6.09%

According to the formula,
Percentage decrease in surface area = [2 x (-24) + (-24) x (-24)/100]%

Correct Option: C

According to the formula,
Percentage decrease in surface area = [2 x (-24) + (-24) x (-24)/100]%
= [-48 + 5.76]% = - 42.24%

Here, n = 100%
According to the formula
Percentage increase in volume = [(1 + n/100)³ - 1] x 100%

Correct Option: D

Here, n = 100%
According to the formula
Percentage increase in volume = [(1 + n/100)³ - 1] x 100%
= [(1 + 100/100)³ - 1] x 100%
= [8 - 1] x 100% = 700%

Volume of solid sphere of radius 4 cm = (4/3)π(4)³ cm³
Volume of hollow sphere = 4/3π[(8)³ - (6)³] cm³

Correct Option: D

Volume of solid sphere of radius 4 cm = (4/3)π(4)³ cm³
Volume of hollow sphere = 4/3π[(8)³ - (6)³] cm³
∵ Weight of 4/3π(4)³ cm³ = 4 kg
= 4(512 - 216)/4³ = 18.5 kg

Volume of prism = Area of base x Height
Weight of prism = volume x density

Correct Option: D

Volume of prism = Area of base x Height
= (1/2) x 10 x 12 x 20
= 1200 cm²

∴ Weight of prism = 1200 x 6
= 7200 g
= 7.2 kg