The number of machines produced by a certain factory in the first half of May completed 45% of the plan for the whole month, and 312 machines were produced in the second half of May. As a result, the production exceeded 10% this month. How many machines were produced in the first half of the month?
某厂五月份上半月生产的机器台数完成了全月计划的45%，下半月生产了312台，结果这个月超产了10%，上半月生产了多少台？
<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">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(11/20) + (1/10)</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">312 / (13/20)</gadget>
<output>480</output>

<gadget id="calculator">480 * (9/20)</gadget>
<output>216</output>

<result>216</result>