In the Red Star Grain Processing Factory, 3 flour mills can grind 16.8 tons of flour in 4 hours. Now it has been increased to 8 flour mills, and it needs to grind 72.8 tons of flour. How many hours does it take?
红星粮食加工厂，3台磨面机4小时可磨面粉16.8吨，现在增加到8台磨面机，要磨面粉72.8吨，需要多少小时？
<gadget id="calculator">16.8 / 3 / 4</gadget>
<output>1.4</output>

<gadget id="calculator">1.4 * 8</gadget>
<output>11.2</output>

<gadget id="calculator">72.8 / 11.2</gadget>
<output>6.5</output>

<result>6.5</result>