Xiao Bin rides a bicycle and travels 15 kilometers per hour, and Xiao Ming walks 5 kilometers per hour. Two people go to a school 30 kilometers away along the same route in a certain place at the same time. When Xiaobin arrived at school, he found that he had forgotten his key, so he went home to get it along the same road, and met Xiaoming on the way. Ask how many kilometers Xiao Ming traveled in total when they met.
小斌骑自行车每小时行15千米，小明步行每小时行5千米．两人同时在某地沿同一条线路到30千米外的学校去上课．小斌到校后发现忘了带钥匙，就沿原路回家去拿，在途中与小明相遇．问相遇时小明共行了多少千米．
<gadget id="calculator">30 + 30</gadget>
<output>60</output>

<gadget id="calculator">15 + 5</gadget>
<output>20</output>

<gadget id="calculator">60 / 20</gadget>
<output>3</output>

<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<result>15</result>