A and B start climbing from the foot of the mountain at the same time, and descend immediately after reaching the top of the mountain. The speed of both of them going down the mountain is 1.5 times of their respective speed of going up the mountain, and A is faster than B. One hour after the two set off, A and B met at a distance of 600 meters from the top of the mountain. When B reached the top of the mountain, A was just halfway up the mountain. So how many hours does it take for A to return to the starting point?
甲、乙两人同时从山脚开始爬山，到达山顶后就立即下山，他们两人的下山速度都是各自上山速度的1.5倍，而且甲比乙速度快．两人出发后1小时，甲与乙在离山顶600米处相遇，当乙到达山顶时，甲恰好到半山腰．那么甲回到出发点共用多少小时？
<gadget id="calculator">4 - 3</gadget>
<output>1</output>

<gadget id="calculator">1_000 / 1</gadget>
<output>1_000</output>

<gadget id="calculator">1_000 * 4</gadget>
<output>4_000</output>

<gadget id="calculator">4_000 - 400</gadget>
<output>3_600</output>

<gadget id="calculator">3_600 - 600</gadget>
<output>3_000</output>

<gadget id="calculator">4_000 * 1.5</gadget>
<output>6_000</output>

<gadget id="calculator">3_000 / 6_000</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 + (1/2)</gadget>
<output>3/2 = around 1.5</output>

<result>3/2 = around 1.5</result>