In order to strengthen the embankment, it is necessary to drive wooden piles into the river. After one wooden pile is inserted into the river (1/5) is exposed to the water surface, and (2/7) is inserted into the soil at the bottom of the river, what percentage is still in the water?
为了加固河堤，需要向河中打入木桩，一根木桩插入河中后(1/5)露出水面，还有(2/7)插入河底的泥土中，还有几分之几在水中？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (1/5) - (2/7)</gadget>
<output>18/35 = around 0.514286</output>

<result>18/35 = around 0.514286</result>