The area of a square is calculated by squaring the length of the sides (multiplying by itself). Therefore, in order to find the length, you must find the square root of 225.
The square root of 225 is 15. Therefore, you length of each side is 15 feet.
p.s. I don't know how old you are, but I would recommend trying to memorise your square numbers up to [tex]17^{2} [/tex] . I know I found that incredibly useful when it came to my exams last year (GCSEs)
