Dig a reservoir with a length of 10 meters and a width of 2.5 meters. To store 100 cubic meters of water, how deep should it be dug?
挖一个蓄水池，长10米，宽2.5米，要使其蓄水100立方米，则应挖多少米深．
<gadget id="calculator">10 * 2.5</gadget>
<output>25</output>

<gadget id="calculator">100 / 25</gadget>
<output>4</output>

<result>4</result>