00:00 Determine the perimeter of the rectangle
00:06 In a rectangle all angles are right angles
00:09 Apply the Pythagorean theorem in triangle ADE
00:12 Insert the appropriate values into the expression and solve to find DE
00:19 Isolate DE
00:30 This is the length of DE
00:42 According to the given data this is an Isosceles triangle
00:48 Opposite sides are equal in a rectangle
00:52 Right angles in a rectangle
00:59 Therefore the triangles are congruent by AAS
01:05 The sides are equal because the triangles are congruent
01:16 The side equals the sum of its parts
01:27 The perimeter of the rectangle equals the sum of its sides
01:37 Let's group the terms together
01:47 Break down 48 into factors of 16 and 3
01:52 Solve the square root of 16
01:56 This is the solution