A batch of coal is shipped from the power plant. It is planned to burn 2 tons per day and burn it out in 40 days. The actual daily saving is 20% compared with the plan. How many days can it actually be burned? (Solve with ratio)
电厂运来一批煤，计划每天烧2吨，40天烧完，实际每天比计划节约20%，实际可以烧多少天？(用比例解)
<gadget id="calculator">2 * 40</gadget>
<output>80</output>

<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">2 * (4/5)</gadget>
<output>8/5 = around 1.6</output>

<gadget id="calculator">80 / (8/5)</gadget>
<output>50</output>

<result>50</result>