There were 2,500 employees in a certain factory, 40% of whom were female employees. After some of them were transferred, female employees accounted for 25% of the total number. How many female employees were transferred?
某工厂原有职工2500人，女职工占40%，调走一部分之后，女职工占总人数的25%，调走了多少女职工？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(3/5) / (3/4)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">2_500 * (4/5)</gadget>
<output>2_000</output>

<gadget id="calculator">2_500 - 2_000</gadget>
<output>500</output>

<result>500</result>