A school used 400 tons of water in September, and saved 20% in October compared with September. How many tons of water was used in October?
某校九月份用水400吨，十月份比九月份节约了20%，十月份用水多少吨？
<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">400 * (4/5)</gadget>
<output>320</output>

<result>320</result>