It cost 240,000 yuan to build a sewage treatment pool, which is 20% less than the original plan. How much was the original plan to invest?
建造一个污水处理池用了24万元，比原计划节省了20%，原计划投资多少元？
<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">24 / (4/5)</gadget>
<output>30</output>

<result>30</result>