The perimeter of a right-angled trapezoid is 32 cm, and the two sides are 4 cm and 5 cm respectively. What is the area of the trapezoid in square centimeters?
一个直角梯形的周长为32厘米，两条腰分别为4厘米和5厘米，梯形的面积为多少平方厘米．
<gadget id="calculator">32 - 4 - 5</gadget>
<output>23</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">23 * 2</gadget>
<output>46</output>

<result>46</result>