Find the perimeter of the quadrangle, the two sides of which are 30mm long, and the other two sides are 20mm long.

In order to find the perimeter of our rectangle, recall the formula for finding the perimeter of a rectangle. P = (a + b) * 2, where P is the perimeter of the rectangle, a is the length of the rectangle, b is the width of the rectangle. Let us have a = 30 mm, b = 20 mm. Next, using the formula, we find the perimeter of our rectangle. (30 + 20) * 2 = 100 (mm.) – the perimeter of the rectangle. We need to express the answer in centimeters. Knowing that there are 10 millimeters in one centimeter. 100 mm = 10 cm.
Answer: 10 centimeters.