20 tons of water is used in September, and 15 tons of water is used in October. What percentage is less in October than in September?
九月份用水20吨，十月份用水15吨，十月份比九月份少百分之几？
<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<gadget id="calculator">5 / 20</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>