Xiaohong walked up the mountain for 1 hour, and he was still 2 kilometers away from the top of the mountain; but it only took him 50 minutes to descend from the top of the mountain. It is known that the speed of Xiaohong going down the mountain is twice the speed of going up the mountain, so how many kilometers is the length of this mountain road?
小红上山走了1小时，距山顶还差2千米；而他从山顶下山只用了50分钟．已知小红下山速度是上山速度的2倍，则这条山路长多少千米．
<gadget id="calculator">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">(5/6) * 2</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">(5/3) - 1</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">2 / (2/3)</gadget>
<output>3</output>

<gadget id="calculator">3 * 1</gadget>
<output>3</output>

<result>3</result>