A factory uses an average of 9 tons of water per day in October, and an average of 8 tons of water per day in November. How many tons less water was used in November than in October?
一个工厂十月份平均每天用水9吨，十一月份平均每天用水8吨．十一月份比十月份少用水多少吨？
<gadget id="calculator">31 * 9</gadget>
<output>279</output>

<gadget id="calculator">8 * 30</gadget>
<output>240</output>

<gadget id="calculator">279 - 240</gadget>
<output>39</output>

<result>39</result>