Teacher Wang rides an electric bike from home to school first uphill and then downhill. The uphill travel is 20 kilometers per hour, and the downhill is 30 kilometers per hour. It takes (1/3) hour for Mr. Wang to go back and forth from home to school. How many kilometers away is Mr. Wang's home from the school?
王老师骑电动车从家去学校先是上坡后下坡，上坡每小时行20千米，下坡每小时30千米，王老师从家到学校往返一次要用(1/3)小时．王老师家离学校多少千米？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) + (1/30)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/3) / (1/12)</gadget>
<output>4</output>

<result>4</result>