A coal mine originally planned to produce 660,000 tons of coal in the first half of the year, but actually produced 22,000 tons more per month than the original plan. According to this calculation, how many months will it take to complete the plan for the first half of the year?
一个煤矿上半年原计划产煤66万吨，实际每月比原计划多产2.2万吨．照这样计算完成上半年计划要几个月？
<gadget id="calculator">66 / 6</gadget>
<output>11</output>

<gadget id="calculator">11 + 2.2</gadget>
<output>13.2</output>

<gadget id="calculator">66 / 13.2</gadget>
<output>5</output>

<result>5</result>