There is a trapezoid with an upper base of 6 cm and a lower base of 10 cm. If only the upper base is extended by 3 cm, the area will increase by 4.5 cm2. Find the area of the original trapezoid.
有一个梯形，上底是6厘米，下底是10厘米，如果只把上底延长3厘米，面积就增加4.5平方厘米，求原来梯形的面积．
<gadget id="calculator">6 + 10</gadget>
<output>16</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">4.5 * (2/3)</gadget>
<output>3</output>

<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">16 * (3/2)</gadget>
<output>24</output>

<result>24</result>