A piece of parallelogram paper has a base of 10cm and a height of 6cm. Cut it into a triangle as large as possible. Calculate the area of the remaining paper.
一张平行四边形的纸，底是10cm，高是6cm，把它剪成一个尽可能大的三角形，求余下的纸张的面积．
<gadget id="calculator">10 * 6</gadget>
<output>60</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * 10 * 6</gadget>
<output>30</output>

<gadget id="calculator">60 - 30</gadget>
<output>30</output>

<result>30</result>