Three cars, A, B, and C, each drive from Shashi to the Western Regions at a certain speed. B starts 5 minutes later than C, and catches up with C 20 minutes after departure. A starts 10 minutes later than B, and A catches up with C 50 minutes after departure. How many minutes does it take for A to catch up with B after starting off?
甲乙丙三辆汽车各以一定的速度从沙市开往西域，乙比丙迟5分钟出发，乙出发后20分钟追上丙，甲比乙迟10分钟出发，甲出发后50分钟追上丙，问甲自出发后需多少分钟才能追上乙？
<gadget id="calculator">10 + 50</gadget>
<output>60</output>

<gadget id="calculator">20 / 25</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) / 50</gadget>
<output>2/125 = around 0.016</output>

<gadget id="calculator">60 * (2/125) * 10</gadget>
<output>48/5 = around 9.6</output>

<gadget id="calculator">60 * (2/125)</gadget>
<output>24/25 = around 0.96</output>

<gadget id="calculator">1 - (24/25)</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">(48/5) / (1/25)</gadget>
<output>240</output>

<result>240</result>