A road is 6 kilometers long, and street lamps should be installed on both sides of the road (both ends must be installed).
一条马路长6千米，在马路的两旁要安装路灯(两端都要安装)，每个50米安一盏，一共需要准备多少盏路灯？
<gadget id="calculator">1_000 / 50</gadget>
<output>20</output>

<gadget id="calculator">6 * 20</gadget>
<output>120</output>

<gadget id="calculator">120 + 1</gadget>
<output>121</output>

<gadget id="calculator">121 * 2</gadget>
<output>242</output>

<result>242</result>