The area of the rectangle is 45 dm, the width is 3 cm. Find the perimeter of the rectangle.

From the very beginning, let’s pay attention to the fact that the area is indicated in dm 2. Therefore, we translate the area into square centimeters:
45 dm 2 = (45 * 100) cm 2 = 4500 cm 2.
Now let’s remember what is the formula for calculating the area of a rectangle:
S = a * b.
From the above formula, we express the length of the rectangle (a):
a = S: b = 4500: 3 = 1500 (cm).
Since we now know the length and width of the rectangle, we can calculate the perimeter:
P = 2 * (1500 + 3) = 3006 (cm).
Answer: the perimeter of the rectangle = 3006 cm.