The length of the sides of the quadrangle is 5 dm 8 dm 9 dm 12 dm find its pyrometer.

As you know, the perimeter of a geometric figure is the sum of the lengths of all sides. Since the quadrilateral has only 4 sides, therefore the perimeter is equal to the sum of the lengths of all four sides. It is known that the lengths of the sides are 5 dm, 8 dm, 9 dm, 12 dm. It turns out that the perimeter can be found as:
5 + 8 + 9 + 12.
It is more convenient to first find the sum of 8 and 12:
5 + 8 + 9 + 12 = 8 + 12 + 5 + 9 = 20 + 5 + 9 = 25 + 9 = 34 dm.
Answer: the perimeter of a rectangle with sides 5 dm, 8 dm, 9 dm, 12 dm is 34 dm.