Install street lamps on both sides of a 400-meter-long road, and install one lamp every 10 meters. How many lamps should be installed in total?
在一条长400米的马路两边安装路灯，每隔10米装一盏，一共要装多少盏．
<gadget id="calculator">400 / 10</gadget>
<output>40</output>

<gadget id="calculator">40 + 1</gadget>
<output>41</output>

<gadget id="calculator">41 * 2</gadget>
<output>82</output>

<result>82</result>