A factory originally planned to burn 65 tons of coal in September, but actually only burned 4/5 of the original plan due to improved technology. How many tons of coal was saved in September?
一个工厂原计划九月份烧煤65吨，由于改进技术，实际只烧了原计划的(4/5)．九月份节约煤多少吨？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">65 * (4/5)</gadget>
<output>52</output>

<gadget id="calculator">65 - 52</gadget>
<output>13</output>

<result>13</result>