Find the middle line of the trapezoid if its base is 19cm and 43.

A trapezoid is a quadrilateral in which two opposite sides are parallel (bases) and the other two are not parallel (sides). If the sides are equal, then the trapezoid is isosceles. If one side is perpendicular to the bases, then the trapezoid is rectangular.
The middle line of the trapezoid is found by the formula:
m = (a + b) / 2,
where a is the larger base of the trapezoid, b is the smaller base of the trapezoid.
Substitute the values given by the condition, and find the length of the middle line of the trapezoid:
m = (19 + 43) / 2 = 62/2 = 31 (cm).
Answer: m = 31 cm.