The power plant used to burn 2.1 tons of coal per day, but now it saves (1/7) less than before. How many tons of coal are saved every day?
发电厂原来每天烧煤2.1吨，现在每天烧煤比原来节约(1/7)．现在每天节约煤多少吨？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">2.1 * (1/7)</gadget>
<output>0.3</output>

<result>0.3</result>