A fish pond is 40 meters long and 30 meters wide. If 200 cubic meters of water are injected into the pond every hour, the fish pond can be filled in 18 hours. How deep is the pond?
一个养鱼池，长40米，宽30米，如果每小时向池内注入200立方米的水，18小时可把养鱼池注满，池深多少米？
<gadget id="calculator">40 * 30</gadget>
<output>1_200</output>

<gadget id="calculator">18 / 1_200</gadget>
<output>3/200 = around 0.015</output>

<gadget id="calculator">200 * (3/200)</gadget>
<output>3</output>

<result>3</result>