A factory produced a batch of products. After the completion (3/7), new technology was introduced, and the efficiency was increased by 25%. The result was 8 days shorter than the scheduled time. Question: How many days did it take to produce this batch of products?
某工厂生产一批产品，在完成(3/7)后，引进了新技术，效率提高了25%，结果比预定时间缩短了8天，问：生产这批产品共用了几天？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 + (1/4)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">1 / (5/4)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 - (3/7)</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">8 / (1/5) / (4/7)</gadget>
<output>70</output>

<gadget id="calculator">70 - 8</gadget>
<output>62</output>

<result>62</result>