A factory burns 4,000 tons of coal in September, and saves 10% in October compared with September. How many tons of coal is burned in October?
某工厂九月份烧煤4000吨，十月份比九月份节约了10%，十月份烧煤多少吨？
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">4_000 * (9/10)</gadget>
<output>3_600</output>

<result>3_600</result>