(Only list the formula (or equation), do not need to calculate) The school organizes hiking activities. The original plan is to walk 3.8km per hour and reach the destination in 3 hours. Actually finished the original distance 0.5 hours ahead of schedule, how many kilometers per hour on average?
(只列式(或方程)，不必计算)学校组织徒步活动，原计划每小时走3.8km，3小时到达目的地．实际提前了0.5小时走完了原定路程，平均每小时走多少千米？
<gadget id="calculator">3.8 * 3</gadget>
<output>11.4</output>

<gadget id="calculator">3 - 0.5</gadget>
<output>2.5</output>

<gadget id="calculator">11.4 / 2.5</gadget>
<output>4.56</output>

<result>4.56</result>