A square has a diagonal with length 12.2. what is the area of the square to the nearest tenth?

The diagonal of a square is related to the length of the side of the square by
[tex]d=\sqrt 2 L[/tex]
where d is the diagonal, and L the length of the side. We are told the diagonal of this square, d=12.2, so we can find the length of the side by rearranging the previous equation:
[tex]L= \frac{d}{ \sqrt{2} } = \frac{12.2}{ \sqrt{2} } =8.6[/tex]

and now we can calculate the area of the square, which is given by the square of the length of the side:
[tex]A=L^2=(8.6)^2=74.0 [/tex]