A road is 450 meters long, and a street lamp is installed every 50 meters (both ends are installed), how many street lamps need to be installed on both sides.
一条马路长450米，每隔50米安一盏街灯(两端都安装)，两侧共需要安多少盏街灯．
<gadget id="calculator">450 / 50</gadget>
<output>9</output>

<gadget id="calculator">9 + 1</gadget>
<output>10</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<result>20</result>