In similar polygons, the corresponding sides have the same ratio.
The first rectangle has a width of 5 meters, and the second rectangle has a width of 15 meters.
The ratio of those two widths is 5/15
Since the rectangles are similar the ratio of the lengths will also be 5/15
So we set up proportions to solve for the length of the second rectangle:
length first rectangle/length of second rectangle = 5/15
7/length 2nd rectangle = 5/15
length of 2nd rectangle = 21 m
