During the National Day holiday, my father took Xiaoliang to climb the mountain. It was 7.8 kilometers from the bottom of the mountain to the top of the mountain. It took them 3 hours to go up the mountain and 2.2 hours to go down the mountain. What is their average speed up and down the hill?
国庆放假，爸爸带着小亮去登山，从山底到山顶共7.8千米，他们上山用了3小时，下山用了2.2小时．他们上下山的平均速度是多少？
<gadget id="calculator">3 + 2.2</gadget>
<output>5.2</output>

<gadget id="calculator">2 / 5.2</gadget>
<output>0.384615</output>

<gadget id="calculator">7.8 * 0.384615</gadget>
<output>2.999997</output>

<result>2.999997</result>