#### Answer

perimeter = $1000$ inches

#### Work Step by Step

RECALL:
(1) The perimeter of a polygon is equal to the sum of the lengths of all its sides.
(2) A square has four equal sides.
This means that the three unknown side lengths are all 250 inches.
Add the lengths of all the sides to find the perimeter:
perimeter = $250+250+250+250= 1000$ inches