What is the name of the symbol used to denote square root?

You can find the constant of proportionality by finding the ratio of

Which number completes the inequality? 2/3 < _ < 7/9

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.