Question 422480
Let x = length of one side of the square photograph.  Since you are looking for the perimeter, you are looking for the distance around the square; and since all of the sides of a square are of equal length, you have:

Perimeter = x + x + x + x = 4x.

The area of any rectangle is length * width.  In your case, since the length and width are equal, {{{Area = x^2}}}.  We know from the problem that Area = 300, so we have:

{{{Area = x^2 = 300}}}
{{{x = sqrt(300)}}}  (Taking the square root of both sides)
{{{x = sqrt(100 * 3) = 10 * sqrt(3)}}}  (simplifying the expression)

The perimeter = {{{4 * 10 * sqrt(3)}}} = {{{40 * sqrt(3)}}} = {{{40 * 1.732}}} = 69.28

Therefore the perimeter of the square photograph is 69.28 inches.