Put 4 identical glass beads into a graduated cylinder filled with 200ml of water, and the water level rises to the position where the mark is 280ml. What is the volume of each glass bead in cubic centimeters?
把4粒相同的玻璃珠子放入盛有200毫升水的量筒里，水面上升到刻度是280毫升的位置．每粒玻璃珠子的体积是多少立方厘米．
<gadget id="calculator">280 - 200</gadget>
<output>80</output>

<gadget id="calculator">80 / 4</gadget>
<output>20</output>

<result>20</result>