Cut out the largest semicircle on a rectangular cardboard with a length of 6 cm and a width of 4 cm. How many square centimeters are left?
在一个长6厘米，宽4厘米的长方形纸板上剪下一个最大的半圆，还剩下多少平方厘米．
<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">3.14 * (9/2)</gadget>
<output>14.13</output>

<gadget id="calculator">24 - 14.13</gadget>
<output>9.87</output>

<result>9.87</result>