The construction team is going to dig a canal, and they have already dug 35.4 meters. The undug is 6.6 meters longer than the dug. How long is this canal in meters?
施工队要挖一条水渠，已经挖了35.4米，没挖的比已挖的多6.6米，这条水渠全长多少米？
<gadget id="calculator">35.4 + 6.6</gadget>
<output>42</output>

<gadget id="calculator">35.4 + 42</gadget>
<output>77.4</output>

<result>77.4</result>