The machine tool factory invested 42 million yuan to build a factory building, saving (1/7) compared to the original plan. How much was the original plan to invest?
机床厂投资4200万元建厂房，比原计划节约了(1/7)，原计划投资多少万元？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 - (1/7)</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">4_200 / (6/7)</gadget>
<output>4_900</output>

<result>4_900</result>