Two people, A and B, start climbing from the foot of the mountain at the same time. When they reach the top of the mountain, they descend immediately. /2). How many meters is the distance from the foot of the mountain to the top of the mountain?
甲乙二人同时从山脚出发开始爬山，到达山顶立即下山，二人下山速度都是上山的2倍，甲到达山顶时，乙离山顶400米，甲回到山脚时，乙下山刚走完(1/2)．山脚到山顶的距离有多少米？
<gadget id="calculator">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">1 - (5/6)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">400 / (1/6)</gadget>
<output>2_400</output>

<result>2_400</result>