The sum of the upper and lower bases of a trapezoid is 15 decimeters and the height is 6 decimeters. What is the area of the trapezoid in square decimeters?
一个梯形的上底与下底的和是15分米，高6分米，这个梯形的面积是多少平方分米．
<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<result>45</result>