The students plant trees on one side of an 80-meter-long highway, one tree every 4 meters (both ends are planted), how many trees should be planted in total.
同学们在一段长80米的公路的一边植树，每隔4米植一棵(两端都植)，一共要植多少棵．
<gadget id="calculator">80 / 4</gadget>
<output>20</output>

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

<result>21</result>