A cylindrical glass tank with a bottom radius of 2 decimeters contains water 1.5 decimeters deep. Put an irregular piece of iron into the tank and completely immerse it in the water. The water surface rises by 0.5 decimeters. The volume of this piece of iron is How many?
一个圆柱形玻璃缸，底面半径为2分米，里面盛有1.5分米深的水，将一块不规则的铁放入水缸中完全浸入水中，水面上升0.5分米，这块铁的体积是多少？
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4 * 0.5</gadget>
<output>6.28</output>

<result>6.28</result>