Put an eraser into a cylindrical tank with a bottom diameter of 4 cm, and the water level rises by 2 cm, find the volume of the eraser.
把一块橡皮放进一个底面直径4cm的圆柱形槽中，水面上升2cm，求这块橡皮的体积．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

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

<gadget id="calculator">3.14 * 4 * 2</gadget>
<output>25.12</output>

<result>25.12</result>