A and B start from the same place at the same time and walk with their backs. A travels an average of 15 kilometers per hour, and B travels an average of 10 kilometers per hour. After walking for 2 hours, A turns around and chases after B. After several hours, A can Catch up with B?
甲、乙两人从同一地点同时出发背向而行，甲平均每小时行15千米，乙平均每小时行10千米，行了2小时后，甲掉头去追乙，经过几小时甲能追上乙？
<gadget id="calculator">15 + 10</gadget>
<output>25</output>

<gadget id="calculator">15 - 10</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">25 * (2/5)</gadget>
<output>10</output>

<result>10</result>