A few days after two road repairing teams jointly repaired a road, team A repaired the full length (1/5), and team B repaired the full length (1/7). The total length of the road is 210 kilometers. rice.
两个修路队合修一条公路几天后，甲队修了全长的(1/5)，乙队修了全长的(1/7)，公路全长210千米，两队共修了多少千米．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/5) + (1/7)</gadget>
<output>12/35 = around 0.342857</output>

<gadget id="calculator">210 * (12/35)</gadget>
<output>72</output>

<result>72</result>