There is 450 ml of water in a measuring cup. A classmate puts a Yuhua stone into the measuring cup. At this time, the scale of the water level rises to 630 ml (the water does not overflow). The space occupied by this Yuhua stone is equivalent to how many milliliters of water occupy space.
一个量杯中装有450毫升的水，一个同学将一块雨花石放人量杯中，此时水面的刻度上升到630毫升(水没有溢出)，这块雨花石所占的空间相当于多少毫升水所占的空间．
<gadget id="calculator">630 - 450</gadget>
<output>180</output>

<result>180</result>