A cylindrical tea barrel, measured from the inside, has a bottom diameter of 4 cm and a height of 15 cm, what is its volume in ml?
一个圆柱形茶叶桶，从里面量，它的底面直径是4厘米，高是15厘米，它的容积是多少ml．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

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

<gadget id="calculator">3.14 * 4 * 15</gadget>
<output>188.4</output>

<result>188.4</result>