VITEEE 2015 Paper

Surface area A of a cube of side x is givenby A = 6x2
On differentiating w.r.t. x, we get

dA

dx

= 12x
Let the change in x be Ax = m% of x
=

mx

100

Change in surface area,
ΔA = (

dA

dx

) Δx = (12x) Δx
= 12 x (

3x

100

) =

12x2m

100

∴ The approximate change in surface area
=

2m

100

×6x2
= 2m% of original surface area