The actual investment of the Beijing 2008 Olympic Games is 3.1 billion, which is 20% less than the original plan. How much is the actual savings?
北京2008奥运会实际投资31亿，比原计划节约了20%，实际比原来节约了多少亿？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">31 / (4/5)</gadget>
<output>155/4 = around 38.75</output>

<gadget id="calculator">(155/4) - 31</gadget>
<output>31/4 = around 7.75</output>

<result>31/4 = around 7.75</result>