Lakeside used 28 tons of water in September, and saved (1/7) in October compared with September. How many tons were saved in October compared with September?
湖滨九月份用水28吨，十月份比九月份节约(1/7)，十月份比九月份节约多少吨？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">28 * (1/7)</gadget>
<output>4</output>

<result>4</result>