The railway from Beijing, the capital of my country, to Yan'an, an old revolutionary base area, is 1581km long. The trains from Beijing to Yan'an run an average of 108km per hour, and have traveled 825km. At this speed, how long will it take for the train to reach Yan'an?
我国首都北京到革命老区延安的铁路长1581km，由北京开往延安的列车平均每时行108km，已经行了825km．照这样的速度，列车还要多少时间才能到达延安？
<gadget id="calculator">1_581 - 825</gadget>
<output>756</output>

<gadget id="calculator">756 / 108</gadget>
<output>7</output>

<result>7</result>