The height of a cylinder is enlarged by 4 times, and the area of the bottom is reduced to 1/2 of the original, so the volume is the same.
一个圆柱的高扩大4倍，底面积缩小到原来的(1/2)，体积就多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">4 * (1/2)</gadget>
<output>2</output>

<result>2</result>