A convoy transported a batch of disaster relief materials. It was originally planned to travel 40 kilometers per hour and reach the disaster area in 7.5 hours. How many hours did it take to reach the disaster area when the actual line was 10 kilometers per hour?
某车队运送一批救灾物资，原计划每小时行40千米，7.5小时到达灾区．实际每小时多行10千米，这样到达灾区用了多少小时？
<gadget id="calculator">40 + 10</gadget>
<output>50</output>

<gadget id="calculator">7.5 / 50</gadget>
<output>0.15</output>

<gadget id="calculator">40 * 0.15</gadget>
<output>6</output>

<result>6</result>