Answer: The required similarity ratio is 2 : 3.
Step-by-step explanation: We are given to find the similarity ratio of the smaller to the larger similar prisms.
The similarity ratio of two similar figures is given by the ratio of the length of a side of the first figure to the length of the corresponding side of the second figure.
For the given similar figures, we have
length of a side of the smaller figure, s = 6 units
and
length of the corresponding side of the larger figure, l = 9 units.
Therefore, the similarity ratio of the smaller prism to the larger figure si given by

Thus, the required similarity ratio is 2 : 3.