What will be the percentage increase in the area of the cube

If you increase a line with %20 it the line will be 1,2/1
If we increase edges with %20 in a surface the area will be 1.2*1.2 =1.44
If we increase edges with %20 in a cube or 3D , the volume is 1.2*1.2 = 1.2*1.2*1.2

Your solution is correct but in order to minimize time to solve

It doesn't matter how many surface have a 3D object or how many edges have a 2D object
So you dont have to think about how many surface does it have.

The ratio of line increase with (100+A)^1
The ratio of area will be (100+A)^2
The ratio of volume will be (100+A)^3



In line the increase or decrease will be also linear. (100+A/100)
In 2D it will be (100+A/100)*(100+A/100) \\ second power
In 3D it will be (100+A/100)*(100+A/100)*(100+A/100) \\third power


All you need to do is just multiply 1.2 * 1.2 = 1.44 and so it is %44
That's all

just like others, even i got 44% increase...but dont know OA says answer is D.....

Now I am sure that it is a mistake in the OA. I changed it to B.

Thank you all for confirming my solution!

I did wrong. I used the volume formula & got wrong answer.

6(10)^2 –> 6(12)^2

(864-600)/600*100=264/6

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

Surface area of a cube = 6a^2
New a = 1.2a
New surface area of the cube = 6 (1.2a)^2 = 1.44 * 6a^2 = 44% increase

IMO B

Cube SA ; 6s^2
s=1 ; CSA ; 6
s=1*1.2 ; CSA ; 6*(1.2)^2
%∆ ; 6*(1.2)^2-6/6 ; ( 1.44-1) ; 44%
IMO B

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