If a tree is planted every 3 meters on both sides of a 90-meter-long road, how many trees can be planted at most?
在一条90米长的道路两边，每隔3米种一棵树，最多可种多少棵树．
<gadget id="calculator">90 / 3</gadget>
<output>30</output>

<gadget id="calculator">30 + 1</gadget>
<output>31</output>

<gadget id="calculator">31 * 2</gadget>
<output>62</output>

<result>62</result>