A road is 900 meters long. Billboards are installed on both sides of the road (both ends are installed), and one billboard is installed every 50 meters. How many billboards are installed in total?
一条公路长900米，在公路两侧安装广告牌(两端都装)，每隔50米装一块，一共安装多少块广告牌？
<gadget id="calculator">900 / 50</gadget>
<output>18</output>

<gadget id="calculator">18 + 1</gadget>
<output>19</output>

<gadget id="calculator">19 * 2</gadget>
<output>38</output>

<result>38</result>