Answer
$6.7$ miles long
Work Step by Step
The Pythagorean theorem is $a^2+b^2=c^2$ to solve for the hypotenuse. We are given that the rectangular park is 6 miles long and 3 miles wide, so we plug in those values to the formula.
$6^2+3^2=c^2$
$36+9=c^2$
$45=c^2$
$c=\sqrt {45}$
$c=3\sqrt 5$
$c\approx6.7$
