The Young Pioneers started planting trees on both sides of the road from the school gate. The road is 210 meters long, and a tree was planted every 10 meters. How many trees were planted in total? (Not planted at the school gate)
少先队员从校门口开始在马路两旁植树，马路全长210米，每隔10米植一棵树，一共植了多少棵树？(校门口不植)
<gadget id="calculator">210 / 10</gadget>
<output>21</output>

<gadget id="calculator">21 * 2</gadget>
<output>42</output>

<result>42</result>