There are 20 boys in class 1, accounting for 1/3 of the whole class. Later, a few girls were transferred away. At this time, girls accounted for 3/5 of the whole class. How many girls were transferred? (What quantity does not change?)
六1班有男生20人，占全班人数的(1/3)，后来又转走几名女生，这时女生占全班的(3/5)，求转走了几名女生？(什么量不变？)
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">20 / (1/3)</gadget>
<output>60</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">20 / (2/5)</gadget>
<output>50</output>

<gadget id="calculator">60 - 50</gadget>
<output>10</output>

<result>10</result>