To dig a canal, 30% of the total length has been dug. If you dig another 25 meters, you will just dig half of the total length. How many meters is this canal?
挖一条水渠，已经挖了全长的30%，如果再挖25米，就正好挖了全长的一半．这条水渠长多少米？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(1/2) - (3/10)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">25 / (1/5)</gadget>
<output>125</output>

<result>125</result>