A primary school uses 220 tons of water this year, saving 30 tons of water compared with last year. What percentage of water is saved this year compared to last year?
某小学今年用水220吨，比去年节约用水30吨，今年比去年节约用水百分之几？
<gadget id="calculator">220 + 30</gadget>
<output>250</output>

<gadget id="calculator">30 / 250</gadget>
<output>3/25 = around 0.12</output>

<result>3/25 = around 0.12</result>