Hello, reiward!

The altitude of a triangle is 30 cm and its base is 80 cm.

Find the area of the trapezoid formed by a line

parallel to the base of the triangle and is 12 cm from the vertex. Code:

B
- *
: *| *
: * | *
: * |12 *
: * | *
30 D *----+---------* E
: * | *
: * | *
: * |18 *
: * | *
- A *---------*-------------------* C
: - - - - - - 80- - - - - - - :

The area of a trapezoid is: .

. . where is the altitude and are the lengths of the parallel sides.

We already know: .

. . We need: .

Since

Therefore: .