It took a person 2 hours to climb a mountain and 2.5 hours to return. He went up the mountain at a speed of 3000 m/h and down the mountain at a speed of 4500 m/h. How many meters does it take to climb this mountain?
某人翻越一座山用了2小时，返回用了2.5小时，他上山的速度是3000米/小时，下山的速度是4500米/小时．问翻越这座山要走多少米？
<gadget id="calculator">2 + 2.5</gadget>
<output>4.5</output>

<gadget id="calculator">1 / 3_000</gadget>
<output>1/3_000 = around 0.000333</output>

<gadget id="calculator">1 / 4_500</gadget>
<output>1/4_500 = around 0.000222</output>

<gadget id="calculator">(1/3_000) + (1/4_500)</gadget>
<output>1/1_800 = around 0.000556</output>

<gadget id="calculator">4.5 / (1/1_800)</gadget>
<output>8_100</output>

<result>8_100</result>