The front face of a square computer monitor consists of a square compu

It is a data sufficiency question so try and establish the sufficiency without actually calculating anything. You have a square frame and inside that, a square screen. The good thing about squares is that the moment you have one bit of data about them, you can calculate anything. Say, if you have any one of diagonal, side, area and perimeter, you can get all the other three.

Say the outside length of the frame is F and the inside length i.e. length of the side of the screen is S.

You know the diagonal of the bigger square so you can get F easily. Diagonal = \(\sqrt{2}\)*Side

So you have the side length, F, of the full monitor.

Question: What is the length of the diagonal of the screen? If you get S, you can easily get Diagonal which is given by the relation shown above. So all you need to know is S.

(1) The frame comprises 1/11 of the side length of the monitor.
Out of F, 1/11 is frame length and 10/11 is screen length. Once you have F, you can get S. Sufficient

(2) Area of frame alone is 42.
We know the total area = \(F^2\)
\(F^2 - S^2 = 42\)
Since we know F, we will get a single value for S (since S cannot be negative). Sufficient.