The areas are different.
Whatever the ratio of perimeters of the similar figures, the areas will be in the ratios squared. Examples: * if the figures have perimeters in a ratio of 1:2, their areas will have a ratio of 1²:2² = 1:4. * If the figures have perimeters in a ratio of 2:3, their areas will have a ratio of 2²:3² = 4:9.
they are related when you can multiply or divide them together and get a whole number
No, in general that is not true. For two similar figures it is true. But you can easily design two different figures that have the same perimeters and different areas, or the same area and different perimeters. For example, two rectangles with a different length-to-width ratio.
if you add up all the sides but in a smart way
First you have to go on stop being a fat kid
If you mean the perimeter or circumference, it depends: different figures may have different perimeters or circumferences, even if they have the same area.
Perimeter will scale by the same factor. Area of the new figure, however is the original figures area multiplied by the scale factor squared. .
Their perimeters are in the same ratio.
The sacle factor between two shapes is the same as the ratio of their perimeters.
"18 perimeters" is is a meaningless phrase since there are no units of measurement. It is like asking how tall are 18 heights?
There is no particular reason. In fact, in general, two shapes will have different areas or perimeters or both.