chronolinkz wrote:

guys, this is straight from the challenge set and i am not following with the explanation. i am so lost with their answer.

a 4 cm cube is cut into 1 cm cubes. what is the percentage increase in the surface area after such cutting?

4%

166%

266%

300%

400%

if you have the challenge set, please refer to question 11 of challenge 1.

i would appreciate if any of you guys can provide insight on this question. and to make matters worst this is just on of the many questions i don't get. its gonna be a longggg month of studying.

The key thing to figure out in this question is that one 4cm cube will be cut into sixty four 1cm cubes to have the same volume, as shown below:

Vol of 1 cube with s 4cm = s^3 = 4*4*4 = 64

Therefore, 64 such cubes of s=1cm are required to have the same volume

Once you figure this out it's simple:

SA of one 4cm cube = 6*4*4

SA of 64 1cm cubes = 64*1*1 = 6*4*4*4

% inc. = [(6*4*4*4)-(6*4*4)]/(6*4*4) * 100

= [6*4*4(4-1)]/6*4*4 *100 = 300%