There are three cars A, B, and C, each driving from point A to point B at a certain speed. B starts 10 minutes later than C, and catches up with C 40 minutes after departure; A starts 20 minutes later than B, and catches up with C 1 hour and 40 minutes after departure. So, how many minutes does it take for A to catch up with B after starting off?
有甲、乙、丙三辆汽车，各以一定的速度从A地开往B地．乙比丙晚出发10分钟，出发后40分钟追上丙；甲比乙又晚出发20分钟，出发后1小时40分钟追上丙．那么，甲出发后需要多少分钟才能追上乙？
<gadget id="calculator">40 / 50</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">130 * (4/5)</gadget>
<output>104</output>

<gadget id="calculator">100 / 104</gadget>
<output>25/26 = around 0.961538</output>

<gadget id="calculator">(25/26) * 20</gadget>
<output>250/13 = around 19.230769</output>

<gadget id="calculator">1 - (25/26)</gadget>
<output>1/26 = around 0.038462</output>

<gadget id="calculator">(250/13) / (1/26)</gadget>
<output>500</output>

<result>500</result>