A section of road is 20 meters long, and trees are planted on both sides of it, one tree every 4 meters, how many trees should be planted in total?
一段路长20米，在它的两旁种树，每4米种一棵，共要种多少棵棵树．
<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<result>12</result>