The "Youth Commando" participated in the mudslide rescue. The original plan was to travel 6 kilometers per hour, and it took 4 hours to reach the destination. They received an urgent notice at the time of departure that they must arrive within 3 hours. How many kilometers do they need to travel on average per hour? (Solve with ratio)
"青年突击队"参加泥石流抢险，原计划每时行6km，要4时才能达到目的地．出发时接到紧急通知要求3时之内必须到达，他们平均每时需行多少千米？(用比例解)
<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<gadget id="calculator">24 / 3</gadget>
<output>8</output>

<result>8</result>