A cube glass container, measure 3 decimeters from the inside, pour 18 liters of water into the container, then submerge an iron block into the water, then measure the water depth in the container to be 2.5 decimeters. What is the volume of this iron block?
一个正方体玻璃容器，从里面量棱长3分米，向容器中倒入18升水，再把一个铁块没入水中，这时量得容器内的水深是2.5分米．这个铁块的体积是多少？
<gadget id="calculator">3 * 3 * 2.5</gadget>
<output>22.5</output>

<gadget id="calculator">22.5 - 18</gadget>
<output>4.5</output>

<result>4.5</result>