The fertilizer plant planned to use 500 tons of water last month, but actually used 450 tons. How much water is saved?
化肥厂上月计划用水500吨，实际用水450吨．节约用水百分之几？
<gadget id="calculator">500 - 450</gadget>
<output>50</output>

<gadget id="calculator">50 / 500</gadget>
<output>1/10 = around 0.1</output>

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