The school planned to use 20 tons of water in September, but actually used only 18 tons. How much water was saved in September?
学校九月份计划用水20吨，实际只用了18吨，九月份节约用水百分之几？
<gadget id="calculator">20 - 18</gadget>
<output>2</output>

<gadget id="calculator">2 / 20</gadget>
<output>1/10 = around 0.1</output>

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