To dig a canal, the number of meters already dug is the undug (2/5), and the length of the undug is 500 meters. How many meters is the total length of this canal?
挖一条水渠，已经挖的米数是未挖的(2/5)，未挖的长度是500米，这条水渠全长多少米？
<gadget id="calculator">2 + 5</gadget>
<output>7</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">500 / (5/7)</gadget>
<output>700</output>

<result>700</result>