Install a street lamp every 10 meters on both sides of a road. It is known that a total of 120 street lamps are installed. How many meters is this road?
在一条路的两旁从头到尾每隔10米装一盏路灯，已知一共装了120盏路灯，这条路有多少米．
<gadget id="calculator">120 / 2</gadget>
<output>60</output>

<gadget id="calculator">60 - 1</gadget>
<output>59</output>

<gadget id="calculator">59 * 10</gadget>
<output>590</output>

<result>590</result>