farm raises 4,500 roosters and hens, of which roosters account for 20% of the total. Later, a batch of hens is shipped back. At this time, the ratio of roosters to the total number is 3:20. How many hens are shipped back to this farm? chicken?
一个养殖场养公鸡和母鸡共4500只，其中公鸡占总数的20%，后来又运回一批母鸡，这时公鸡与总数的比是3：20，这个养殖场又运回多少只母鸡？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3 / 20</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(1/5) / (3/20)</gadget>
<output>4/3 = around 1.333333</output>

<gadget id="calculator">4_500 * (4/3)</gadget>
<output>6_000</output>

<gadget id="calculator">6_000 - 4_500</gadget>
<output>1_500</output>

<result>1_500</result>