In September, 20 tons of water is used, and in October, water is saved by 20% compared with September. How many tons of water is used in October?
九月份用水20吨，十月份用水比九月份节约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">20 * (4/5)</gadget>
<output>16</output>

<result>16</result>