Answer:
30√74 ft or 258.070 ft rounded to three decimal places.
Explanation:
To find the length of a diagonal, add the square of the width and the square of the length together and find the square root of the sum.
d = √210² + 150²
d = √44100 + 22500
d = √66600
d = 258.069758 ft (This is the answer I got in six decimal places. Rounding it to three, as it says in the question, would be 258.07 ft, as 7 is greater than 5 (the third digit was 9 by the way).)
An exact answer to that, in radical form, is 30√74 ft.