The school planted a total of 80 poplar trees on both sides of the playground, one at each end, and the distance between each two trees is 6.5m. How long is the playground in meters?
学校在操场的两边一共栽了80棵杨树，两端都栽1棵，每两棵之间的距离是6.5m，操场的长是多少米？
<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<gadget id="calculator">40 - 1</gadget>
<output>39</output>

<gadget id="calculator">39 * 6.5</gadget>
<output>253.5</output>

<result>253.5</result>