On a road, a tree is planted every 5 meters, and 9 trees have been planted. Calculate the distance between the first tree and the ninth tree?
一条公路上，每隔5米种一棵树，已经种了9棵，算一算第一棵与第九棵相距几米？
<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">8 * 5</gadget>
<output>40</output>

<result>40</result>