To determine which of the given expressions is rational, let's analyze each one:
-
\( \sqrt{3} \times \sqrt{3} \) = \( 3 \) (this is rational)
-
\( \frac{1}{\sqrt{3}} \) (this is not rational because it's not a terminating or repeating decimal).
-
\( \frac{\sqrt{3}}{1} \) = \( \sqrt{3} \) (this is not rational).
-
\( \sqrt{3} + \sqrt{3} \) = \( 2\sqrt{3} \) (this is not rational).
From the analysis above, the only rational expression is:
\( \sqrt{3} \times \sqrt{3} = 3 \).