In a glass tank with a length of 50 cm and a width of 40 cm, put a square iron block with a side length of 10 cm, and the water depth at this time is 20 cm. If the iron block is taken out of the water, the water depth in the tank is how many centimeters?
在一只长50厘米，宽40厘米的玻璃缸中，放入一块棱长为10厘米的正方体铁块，这时水深为20厘米，如果把这块铁块从水中取出，缸中的水深是多少厘米？
<gadget id="calculator">50 * 40 * 20</gadget>
<output>40_000</output>

<gadget id="calculator">10 * 10 * 10</gadget>
<output>1_000</output>

<gadget id="calculator">40_000 - 1_000</gadget>
<output>39_000</output>

<gadget id="calculator">50 * 40</gadget>
<output>2_000</output>

<gadget id="calculator">39_000 / 2_000</gadget>
<output>39/2 = around 19.5</output>

<result>39/2 = around 19.5</result>