On both sides of the 180-meter-long road, a willow tree is planted every 9 meters. If both ends are planted, how many willow trees will be planted in total?
在长180米的公路两旁，每隔9米栽柳树1棵．两端都种，一共要栽柳树多少棵？
<gadget id="calculator">180 / 9</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>