Question

a rectangular park is 4 miles long and 2 miles wide. how long is pedestrian route that runs diagonally across the park

Answer 1

You can use the Pythagorean theorem to solve this
${x}^{2} = {4}^{2} + {2}^{2}$
Now solve for x
${x}^{2} = 16 + 4 \\ {x}^{2} = 20 \\ x = \sqrt{20}$
Now you can simplify this to
$x = \sqrt{5 \times 4} \\ x = \sqrt{5} \sqrt{4} \\ x = \sqrt{5 } \times 2 \\ x = 2 \sqrt{5}$
And that's your answer