The figures are similar. 15:18 or 5:6. Find the ratio of their perimeters and the ratio of their areas.

Ratio of perimeter (linear measure) is the same as the scale factor (5:6).

Ratio of area (unit squared) is the square of the ratio, namely 5^2:6^2=25:36

Ratio of volume (unit cubed) is the cube of the ratio, namely 5^3:6^3=125:216