A 3.5-meter-long bamboo pole is vertically inserted into a pool. The part of the bamboo pole that enters the mud is 0.4 meters, and the part that is exposed to the water is 0.8 meters. How many decimeters is the depth of the pool.
一根3.5米长的竹竿垂直插入水池中，竹竿的入泥部分是0.4米，露出水面的部分是0.8米．池水深多少分米．
<gadget id="calculator">3.5 - 0.4 - 0.8</gadget>
<output>2.3</output>

<result>2.3</result>