Use a rope to measure the depth from the well platform to the well water surface. Fold the rope in half and hang it to the well water surface. The rope exceeds the well platform by 9 meters. Fold the rope in three and hang it to the well water surface. The rope exceeds the well platform by 2 meters. What is the length of the rope?
用一根绳子测井台到井水面的深度，把绳对折后垂到井水面，绳子超过井台9米，把绳子三折后垂到井水面，绳子超过井台2米，绳长为多少？
<gadget id="calculator">9 - 2</gadget>
<output>7</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/2) - (1/3)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">7 / (1/6)</gadget>
<output>42</output>

<result>42</result>