Bunuel wrote:

gmatpapa wrote:

What is the area of a square that has a diagonal of length 10?

A. 5

B. 10

C. 20

D. 40

E. 45

Source: Cliff's GMAT

\(area_{square}=side^2=\frac{diagonal^2}{2}\): so A to be the answer either option A should read 50 instead of 5 or diagonal should be \(\sqrt{10}\) instead of 10.

Yes. Answer quite clearly should be 50.

Does this OE make sense to you:

From the relationship that exists in a right triangle, we see that the sides of the square

must equal the square root of 5. Thus the area of the square is 5As OE says that \(side=\sqrt{5}\) then there must be the second case I suggested: diagonal should be \(\sqrt{10}\) instead of 10.