There is a 100-meter-long road in front of the school. A total of 42 trees are planted on both sides of the road. The distance between two adjacent trees on each side is equal, and both ends of the road are planted. Excuse me: What is the distance between the trees?
学校门前有条长100米的马路，马路两侧一共种了42棵树，每侧相邻两棵树之间的距离都相等，而且马路的两端都种了，请问：相邻两棵树之间的距离是多大？
<gadget id="calculator">42 / 2</gadget>
<output>21</output>

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

<gadget id="calculator">100 / 20</gadget>
<output>5</output>

<result>5</result>