The greening team originally planned to plant a tree every 9 meters on one side of the road, and a total of 81 trees could be planted including the two ends. The plan was changed today, and 121 trees were planted equidistantly. Find the distance between the two trees now.
绿化组原计划在马路的一侧每隔9米种一棵树，连两头在内共能种81棵树．今改变计划，结果用等距离种树121棵．求现在两树之间的棵距．
<gadget id="calculator">81 - 1</gadget>
<output>80</output>

<gadget id="calculator">121 - 1</gadget>
<output>120</output>

<gadget id="calculator">9 / 120</gadget>
<output>3/40 = around 0.075</output>

<gadget id="calculator">80 * (3/40)</gadget>
<output>6</output>

<result>6</result>