A washing and dyeing factory plans to use 400 tons of water in the first half of the year, but actually saves (1/5) compared to the plan. How many tons does it actually use?
某洗染厂，上半年计划用水400吨，实际比计划节约了(1/5)，实际用水多少吨？
<gadget id="calculator">1 / 5</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">400 * (4/5)</gadget>
<output>320</output>

<result>320</result>