Someone runs along a row of trees at the same speed, and it takes 30 seconds to run from the first tree to the sixth tree (the distance between every two trees is equal, and the number of trees is enough), if running for 120 seconds, How many trees should he run to?
某人以相同的速度沿着一排树跑步，从第1棵跑到第6棵共用了30秒(每两棵树之间的距离相等，树的数量足够多)，如果跑了120秒，他应该跑到了第多少棵树．
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">30 / 5</gadget>
<output>6</output>

<gadget id="calculator">120 / 6</gadget>
<output>20</output>

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

<result>21</result>