Arbor Day is here, and the young pioneers are going to plant 8 poplar trees between two buildings 72 meters apart. If the two ends are not planted, what is the average distance between every two trees?
植树节到了，少先队员要在相距72米的两栋楼房之间种8棵杨树，如果两头不栽，平均每两棵树之间的距离应是多少？
<gadget id="calculator">8 + 1</gadget>
<output>9</output>

<gadget id="calculator">72 / 9</gadget>
<output>8</output>

<result>8</result>