The distance from the foot of the mountain to the top of the mountain is 12 kilometers. A tourist goes up to the top of the mountain at a speed of 4 kilometers per hour, and then immediately returns on the same road. It is known that his average speed of going up and down the mountain is 4.8 kilometers per hour. Find the time for the tourist to go down the mountain.
山脚到山顶有12千米，一个游客以4千米/时的速度上到山顶，又立即按原路返回，已知他上、下山的平均速度是4.8千米/时．求这位游客下山的时间．
<gadget id="calculator">24 / 4.8</gadget>
<output>5</output>

<gadget id="calculator">12 / 4</gadget>
<output>3</output>

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

<result>2</result>