A canal in a certain town was built. 45% of its total length was built in the first month, 1120 meters in the second month, and 640 meters remained unrepaired. How long is the canal in meters?
某乡修一条水渠，第一个月修了全长的45%，第二个月修了1120米，还剩640米没有修，这条水渠全长多少米？
<gadget id="calculator">1_120 + 640</gadget>
<output>1_760</output>

<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (9/20)</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">1_760 / (11/20)</gadget>
<output>3_200</output>

<result>3_200</result>