Find the perimeter of the rectangle if its width is 8dm and the area is 72dm.

First of all, we express the length of the rectangle from the formula to determine its area. We know that S = a * b. To find the first factor, divide the product by the second:
a = S: b.
According to the condition of the assignment, S = 72 dm², b = 8 dm.
Therefore, a = 72: 8 = 9 dm.
The perimeter is the sum of all sides, for such a figure it corresponds to the formula:
P = 2a + 2b = 2 * 9 + 2 * 8 = 18 + 16 = 34 dm.