The power plant used 800 tons of coal in April, 20% less than in March. How many tons of coal was used in March?
发电厂四月份用煤800吨，比三月份节约20%，三月份用煤多少吨？
<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">800 / (4/5)</gadget>
<output>1_000</output>

<result>1_000</result>