Step-by-step explanation:
Let the dimension of the box be x, y and z.
Volume of the box V = xyz
Since the box is a rectangular box, the base will be a square of equal length.
V = x²h where h is the height of the box
If the sum of the length, width, and height equals 180, then x+x+h = 180
2x+h = 180
h = 180-2x
Substitute h = 180-2x into the volume of the box
V = x²(180-2x)
V = 180x²-2x³
The box has its maximum volume when
Since 2x+h = 180
Substitute x = 60 into the equation ang get the height h
2(60)+h = 180
120+h = 180
h = 180-120
h = 60
Hence the dimension of the rectangular box is 60 by 60 by 60
