In September, the Chinese canteen of Jiangbei Elementary School planned to burn 3.5 tons of coal. Due to the improvement of coal burning technology, only the planned amount was actually used (5/7). How many tons of coal was actually burned in September?
江北小学中餐食堂九月份计划烧煤3.5吨，由于改进烧煤技术，实际看只用了计划的(5/7)．九月份实际烧煤多少吨？
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">3.5 * (5/7)</gadget>
<output>2.5</output>

<result>2.5</result>