Cars A and B are chasing a person in front at the same time at the same time. A's speed is 21m/s, B's speed is 16m/s, and pedestrian's speed is 1m/s. It takes 72s for A to catch up. How long does it take for B to catch up?
甲、乙两车在同一地点同时间追前面一个人，甲速21m/s，乙速16m/s，行人速度1m/s，甲追上用了72s，乙追上需多久？
<gadget id="calculator">21 - 1</gadget>
<output>20</output>

<gadget id="calculator">20 * 72</gadget>
<output>1_440</output>

<gadget id="calculator">16 * 72</gadget>
<output>1_152</output>

<gadget id="calculator">1_440 - 1_152</gadget>
<output>288</output>

<gadget id="calculator">16 - 1</gadget>
<output>15</output>

<gadget id="calculator">288 / 15</gadget>
<output>96/5 = around 19.2</output>

<gadget id="calculator">(96/5) + 72</gadget>
<output>456/5 = around 91.2</output>

<result>456/5 = around 91.2</result>