There is a road 800 meters long in the newly built Beichuan County. How many saplings are needed to plant a tree every 20 meters on both sides of the road?
新建的北川县城里有一条长800米的马路．在马路的两侧从头到尾每隔20米栽一棵树，一共需要多少棵树苗？
<gadget id="calculator">800 / 20</gadget>
<output>40</output>

<gadget id="calculator">40 + 1</gadget>
<output>41</output>

<gadget id="calculator">41 * 2</gadget>
<output>82</output>

<result>82</result>