Let's call Length 'L'. And call Width 'W'. We know that the Length is 4 times the Width so we can say L = 4W. In order to really calculate the perimeter, we first need to find out what W is, because L depends on W (because it is 4W).
Area = 4W × W 256 = 4W². 256 ÷ 4 = W² 64 = W² √64 = W 8 = W
Now we can finally find out the perimeter! L is 4W = 4(8) = 32.
Perimeter = 2L + 2W Peri = 2(32) + 2(8) Peri = 64 + 16 = 80.