The side of the square is 36 cm. Find the area of a rectangle whose perimeter is equal to the perimeter of the square.

Find the perimeter of the square
P = 4a = 36 * 4 = 144cm
Now remember the condition of a rectangle, which is essentially a square in which two opposite sides are the same – we take them for A and B. The perimeter of the rectangle is
P = 2 * (A + B) = 144cm (by condition)
Find the values of A and B
A + B = 144/2 = 72cm
A = 72- B
B = 72-A
Then we substitute these values into the formula for the area of a rectangle
S = A * B
S = A * (72-A)
S = 72A-A2