The school road is 100 meters long, and a tree is planted every 5 meters on both sides of the road (both ends are planted), how many trees are planted in total?
学校马路长100米，在马路两旁每隔5米栽一棵树，(两端都栽)，一共栽多少棵．
<gadget id="calculator">100 / 5</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>