Xiaohong’s house used to use 11 tons of water per month, but after replacing the water-saving faucet, it used 9 tons of water per month.
小红家原来每月用水11吨，更换了节水龙头后每月用水9吨，每月用水比原来节约了几分之几？
<gadget id="calculator">11 - 9</gadget>
<output>2</output>

<gadget id="calculator">2 / 11</gadget>
<output>2/11 = around 0.181818</output>

<result>2/11 = around 0.181818</result>