Install street lamps on both sides of a 100-meter-long road (both ends must be installed), and install one lamp every 5 meters. How many lamps should be installed in total?
在一条长100米的道路两侧安装路灯(两端都要安装)，每隔5米安装一盏，一共要安装多少盏灯？
<gadget id="calculator">100 / 5</gadget>
<output>20</output>

<gadget id="calculator">20 + 1</gadget>
<output>21</output>

<gadget id="calculator">21 * 2</gadget>
<output>42</output>

<result>42</result>