Dad took Xiaoyong to climb mountains on weekends. They traveled from the bottom of the mountain to the top of the mountain in 3 hours at a speed of 2.4 kilometers per hour. The speed of going down the mountain on the original road was accelerated, and they traveled 3.6 kilometers per hour. Find their average speed up and down the hill.
双休日爸爸带小勇去登山．他们用每小时2.4千米的速度，3小时从山底到了山顶，原路下山速度加快，每小时行3.6千米．求他们上山下山的平均速度．
<gadget id="calculator">2.4 * 3</gadget>
<output>7.2</output>

<gadget id="calculator">7.2 / 3.6</gadget>
<output>2</output>

<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">7.2 / 5</gadget>
<output>1.44</output>

<gadget id="calculator">2 * 1.44</gadget>
<output>2.88</output>

<result>2.88</result>