The bus from Xiaoshan to Hangzhou departs every 30 minutes. Teacher Chen originally wanted to take the 8:10 bus to Hangzhou. Due to some delays, Mr. Chen arrived at the station at 9:00. Please do the math, how long will Mr. Chen have to wait at the station to get on the next bus?
从萧山到杭州的汽车每隔30分钟开出一班，陈老师原来想搭乘8：10的那一班车去杭州．由于有事耽搁了，陈老师到达车站已经是9：00．请你算一算，陈老师要在车站等多长时间才能乘上下一班车？
<gadget id="calculator">30 - 20</gadget>
<output>10</output>

<result>10</result>