The length of the rectangle is 15 dm, the area is 90 dm². How much is the width of the length?

Given:
The length a of the rectangle is 15 decimetres.
The area S of the figure is 90 dm2.

Let’s find what the width of the quadrangle is equal to by the formula b = S: a:
b = S: a = 90: 15 = 6 decimeters.
The length is 100%.
Let’s find how much of the length is the width by writing the following proportion:
15 dm – 100%
6 dm – x%
x = 100 * 6: 15 = 40%
Answer: the width of the length is 40%.