A rectangular prism is a polyhedron with six rectangular faces. To fully define a rectangular prism, one must know its length, width and height. The volume of a rectangular prism is expressed as the product of its dimensions - length, width and height. To calculate for its width, we use the volume formula.
V = l x w x h
From the given, we have:
l = 3w
h = 2 + w
V = 135 ft^3
Substituting the given expressions,
135 ft^3 = 3w (w) (2+w)
135 ft^3 = 6w^2 + 3w^3
Solving for w, we obtain the following values:
w1= 3
w2 = 2.5 + 2.96i
w3 = 2.5 - 22.96i
Since width should not have a negative value, the value of w should be 3 ft.