A bamboo pole is inserted into the bottom of the pool, and the part above the water is 5 meters long. Put the bamboo pole upside down and insert it into the bottom of the pool, and 2 meters above the water surface is dry. Find the length of this bamboo pole.
一根竹竿插入水池底部，露出水面部分长5米．把竹竿倒过来插入水池底部，露出水面部分有2米是干的．求这根竹竿的长度．
<gadget id="calculator">5 - 2</gadget>
<output>3</output>

<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<result>8</result>