Xiaoming’s family used 40 tons of water last year, but this year they saved 4 tons compared to last year. What percentage did they save?
小明家去年用水40吨，今年比去年节约了4吨，节约了百分之几？
<gadget id="calculator">4 / 40</gadget>
<output>1/10 = around 0.1</output>

<result>1/10 = around 0.1</result>