Measure the volume of the stone with a measuring cup. Before the stone is placed, the volume of water is 350 cubic centimeters. After the stone is placed, the total volume of water is 420 cubic centimeters. What is the volume of the stone?
用量杯测量石块的体积，放入石块前，水的体积是350立方厘米，放入石块后，水的总体积是420立方厘米，那么石块的体积是多少．
<gadget id="calculator">420 - 350</gadget>
<output>70</output>

<result>70</result>