On both sides of a 200-meter-long road, a tree is planted every 10 meters from the beginning to the end, how many trees are planted in total?
在一条长200米的公路两侧，从头到尾每隔10米栽一棵树，一共栽树多少棵棵．
<gadget id="calculator">200 / 10</gadget>
<output>20</output>

<gadget id="calculator">20 + 1</gadget>
<output>21</output>

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

<result>42</result>