A poplar tree is planted every 9 meters on both sides of a road (both ends must be planted), and a total of 280 trees are planted. How long is the road in meters?
在一条公路的两旁每隔9米栽一棵杨树(两端都要栽)，一共栽了280棵，这条公路长多少米．
<gadget id="calculator">280 / 2</gadget>
<output>140</output>

<gadget id="calculator">140 - 1</gadget>
<output>139</output>

<gadget id="calculator">139 * 9</gadget>
<output>1_251</output>

<result>1_251</result>