The area of a rectangular forest area is 27 km2, its length is 9 km, find the perimeter of the forest area.

Let us express the width of a rectangular forest area, when its area is known, equal to 27 km² and length = 9 km. Since the area is calculated by the formula:

S = a * b, therefore:

b = S: a = 27: 9 = 3 km.

Let’s find the perimeter of this territory, according to the formula:

P = 2a + 2b. Substitute the known values and write the expression:

P = 2 * 9 + 2 * 3 = 18 + 6 = 24 km.