JubtaGubar wrote:

What will be the percentage increase in the area of the cube's surface if each of the cube's edges grows by 20%?

(A) 33%

(B) 44%

(C) 55%

(D) 56%

(E) 73%

The question is very easy. My logic is the following:

A surface = 6*a^2

After 20% increase A surface = 6* ((1.2a)^2) = 6*1.44*a^2

The increase in the surface area = (6*1.44*a^2 - 6*a^2)/6*a^2 = (6*a^2(1.44-1))/(6*a^2) = 1.44-1=0.44 = 44%

but the official answer is different...

Could you please advise what is wrong with my solution or the official answer is not correct?

Your solution is correct.

Percent increase=change/original=(6*144-6*100)/(6*100)*100=44%.

Or directly: the new surface area is 6*144=(6*100)*1.44 --> increase 44%.