The actual investment of the National Stadium (Bird's Nest), the main venue of the Beijing Olympic Games, is about 3.1 billion yuan, which is 7/38 less than the original plan. How much is the original plan to invest?
北京奥运会主会场--国家体育场(鸟巢)实际投资约为31亿元，比原计划节约了(7/38)，原计划投资多少亿元？
<gadget id="calculator">7 / 38</gadget>
<output>7/38 = around 0.184211</output>

<gadget id="calculator">1 - (7/38)</gadget>
<output>31/38 = around 0.815789</output>

<gadget id="calculator">31 / (31/38)</gadget>
<output>38</output>

<result>38</result>