A shoe factory produces leather shoes. The number of pairs produced in October is more than that in September (1/4). If 20,000 pairs are produced in October, how many pairs will be produced in September?
某鞋厂生产皮鞋，十月份生产的双数比九月份多(1/4)，十月份生产20000双，九月份生产多少双？
<gadget id="calculator">1 / 4</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">20_000 / (5/4)</gadget>
<output>16_000</output>

<result>16_000</result>