The children planted 10 trees on one side of the road, and the teacher asked them to place another tree between every two trees. How many trees will there be after planting?
小朋友在公路的一边栽了10棵树，老师让他们在每两棵树之间再载一棵树，那么栽完之后一共有多少棵树．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">9 + 10</gadget>
<output>19</output>

<result>19</result>