The waist length of an isosceles trapezoid is 6cm, the circumference is 30cm, and the height is 5cm. What is the area of the isosceles trapezoid in square centimeters?
一个等腰梯形的腰长6cm，周长30cm，高是5cm，等腰梯形的面积是多少平方厘米？
<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<gadget id="calculator">30 - 12</gadget>
<output>18</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">18 * (5/2)</gadget>
<output>45</output>

<result>45</result>