Xiaoqing walks 100 meters per minute, Xiaosong walks 120 meters per minute, the two walk in opposite directions at the same time, and after 5 minutes, Xiaosong turns to chase Xiaoqing. How many minutes for Xiao Song to catch up with Xiao Qing?
小清每分钟走100米，小松每分钟走120米，两人同时同地向相反方向走去，5分钟后，小松转向追小清．小松几分钟追上小清？
<gadget id="calculator">100 + 120</gadget>
<output>220</output>

<gadget id="calculator">120 - 100</gadget>
<output>20</output>

<gadget id="calculator">5 / 20</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">220 * (1/4)</gadget>
<output>55</output>

<result>55</result>