Answer: 4.5 inches
Explanation:
The volume of a rectangular prism is given by ;-
, where l is length , w is width and h is height of the rectangular prism.
Given : V= 138.24 cubic inches, h= 9.6 inches , l = 3.2 inches
Substitute these values in the above formula , we get :-

Therefore , the width of the prism = 4.5 inches.