A truck went to the disaster area to deliver relief supplies and traveled 30km in 2 hours. It is 90km from the starting point to the disaster area. According to this speed, how many hours will it take for the whole journey.
一列货车前往灾区运送救灾物资，2小时行驶了30km．从出发点到灾区有90km，按照这样的速度，全程需要多少小时．
<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">90 / 15</gadget>
<output>6</output>

<result>6</result>