A school wants to plant 21 palm trees (one must be planted at both ends) beside a 100-meter-long school road. What is the distance between every two palm trees?
某校要在100米长的校道旁种21棵棕树(两端必须种一棵)，每两棵棕树的间隔应是多少米．
<gadget id="calculator">21 - 1</gadget>
<output>20</output>

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

<result>5</result>