A computer manufacturer claims that a perfectly square computer

Corrected the options.

i think technically, the question is wrongly written...when someone says that diagonal of the monitor is X, it means the diagonal of the screen. check online for all major brands by what is meant when diagonal size is given.
i understood the question wrong just because of this shift in meaning.

I redone the question after few months...still think the question is written incorrectly.

I am confused regarding the wordings here. Could some one explain how we can use the relation stated here "area of screen is three times the size of the frame. Does it mean area of the screen is thrice than the area of frame. Confused with the word " Size". VeritasPrepKarishma

Yes, it means {the area of the screen } = 3*{the area of the frame}.

Since the diagonal = side√2, we have:

20 = side√2

20/√2 = side

Multiplying by √2/√2, we have:

10√2 = side

If we let each side of the monitor, not counting the frame = n, then we can create the following equation:

n^2 = 3[(10√2)^2 - n^2]

n^2 = 3[200 - n^2]

n^2 = 600 - 3n^2

4n^2 = 600

n^2 = 150

n = √150

So, the diagonal of the screen is √150 x √2 = √300.

Alternate Solution:

Since the diagonal = side√2, a side of the monitor is 20/√2 = 10√2. Thus, the area of the monitor, including the screen and the surrounding frame, is (10√2)^2 = 200.

If we let A denote the area of the surrounding frame, the area of the screen is 3A and thus, the total area of the monitor is 3A + A = 4A. Since 4A = 200, we find that A = 50 and the area of the screen is 3A = 150. Then, a side of the screen is √150 = 5√6. Finally, the diagonal of the screen is (5√6) x √2 = 5√12 = √300.

Answer: E

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