The perimeter of an isosceles trapezoid is 150 cm, and the lateral side is 30 cm. Find the midline of the trapezoid.

The sides of an isosceles trapezoid are equal, the sum of the lengths of the bases a and b is equal to the difference between the perimeter of the trapezoid P and the lengths of the sides with:

a + b = P – 2 * c = 150 – 2 * 30 = 150 – 60 = 90 cm.

The middle line of trapezoid m is equal to half the sum of the lengths of bases a and b:

m = (a + b) / 2 = 90/2 = 45 cm.