To build a canal, 40% of the total length was built on the first day, and 600 meters on the second day, and the canal was just repaired in two days (9/10). How long is this canal in meters?
修一条水渠，第一天修了全长的40%，第二天修了600米，两天正好修了这条水渠的(9/10)．这条水渠全长多少米？
<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(9/10) - (2/5)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">600 / (1/2)</gadget>
<output>1_200</output>

<result>1_200</result>