Liu Qi used a rope to measure the depth of a dry well. He put one end of the rope into the bottom of the well, and the rope was 10 meters long outside the wellhead; The rope still has 2 meters. How deep is this dry well?
刘奇用一根绳子测量一口枯井的深度，他把绳子的一端放入井底，井口外绳子长10米；他把这根绳子对折后，将一端再放入井底，这时在井口外的绳子还有2米．这口枯井有多深？
<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<gadget id="calculator">2 - 1</gadget>
<output>1</output>

<gadget id="calculator">6 / 1</gadget>
<output>6</output>

<result>6</result>