The middle line of the trapezoid is 10 cm and one of the bases is 15 cm. Find the other base.

A trapezoid is a quadrangle in which only two sides are parallel and all sides are of different lengths.

The middle line is the segment that connects the mid-sides of the trapezoid. It is parallel to its bases and equal to their half-sum:

m = (BC + AD) / 2.

In order to find the length of the second base, we first find their sum. To do this, you need to double the length of the middle line:

(BC + AD) = m 2;

(ВС + АD) = 10 2 = 20 cm.

Now, to calculate the base of the BC, we find the difference between the sum of the bases and the base of AD:

BC = (BC + AD) – AD;

BC = 20 – 15 = 5 cm.

Answer: the length of the base of the BC is 5 cm.