Pippi climbs the mountain at a speed of 3 kilometers per hour, and when he reaches point A on the way, he reduces his speed to 2 kilometers per hour. In the next 1 hour, he walked to the top of the mountain, went down immediately, and walked to a place 200 meters above point A. If he goes down the mountain at a speed of 4 kilometers per hour, it takes 42 minutes less to go down the mountain than to go up the mountain. So, how many kilometers did he walk back and forth?
皮皮以每小时3千米的速度登山，走到途中A点，他将速度降为每小时2千米．在接下来的1小时中，他走到山顶，又立即下山，并走到A点上方200米的地方．如果他下山的速度是每小时4千米，下山比上山少用了42分钟．那么，他往返共走了多少千米．
<gadget id="calculator">0.2 + 4</gadget>
<output>4.2</output>

<gadget id="calculator">4.2 / 6</gadget>
<output>0.7</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / (1/4)</gadget>
<output>8</output>

<gadget id="calculator">0.7 * 8 * 2</gadget>
<output>11.2</output>

<result>11.2</result>