First, we know the area of a square is side length side length = Area. For this square, the area would be:
18*18=A
324 = A
Now that we know the area that is being referened, we can look at the formula for the area of a rectangle, which is width * length = Area. We know the length and we know the area, so we can fill in these known values and solve for the unknown width.
w*l = A
w*6=324
w=324/6
w=54
So our rectangle has the width of 54 and the length of 6. Lastly, the formula for perimeter is 2w + 2l = P. We can again fill in our knowns and solve for the unknown.
2(54) + 2(6) = P
108 + 12 = P
120 = P
The perimeter of the rectangle is 120 cm.