KillerSquirrel wrote:

You can put 64 1cm cubes into 4cm cube. since 4^3 = 64 and 1^3 = 1.

64/1 = 64

the surface area of 4cm cube is 4^2*6 = 96. the surface area of 1cm cube is 1^2*6 = 6 but we have 64 cubes.

64*6/96 = 4 = 400% so the answer is (E)

PLUS to the KS explanation,

(64*6 - 96) / 96 = 4-1 = 3 we are speaking about percentage so multiply by 100%, we get 300 %.

we need to deduct one, cuz the stem is asking percentage

increase.