Install street lamps (both ends) on one side of a 600-meter-long road, and install one lamp every 30 meters. How many street lamps should be installed in total?
在一条长600米的马路一边安装路灯(两端都装)，每隔30米装1盏，一共要装多少盏路灯？
<gadget id="calculator">600 / 30</gadget>
<output>20</output>

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

<result>21</result>