Ding Ding went to Nanshan to play. It took 20 minutes to go uphill, with an average of 35 meters per minute; it took 10 minutes to go downhill, with an average of 50 meters per minute. How many meters per minute did Ding Ding walk from his home to Nanshan on average?
丁丁去南山游玩，上坡用了20分钟，平均每分钟走35米；下坡用了10分钟，平均每分钟走50米．丁丁从家到南山平均每分钟走多少米？
<gadget id="calculator">35 * 20</gadget>
<output>700</output>

<gadget id="calculator">50 * 10</gadget>
<output>500</output>

<gadget id="calculator">700 + 500</gadget>
<output>1_200</output>

<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<gadget id="calculator">1_200 / 30</gadget>
<output>40</output>

<result>40</result>