There were originally 48 students in a class, 30 boys, and then a few girls were transferred. At this time, the number of girls accounted for 40% of the whole class.
一个班原来有48人，男生有30人，后来又转来多少个女生，这时女生人数占全班人数的40%．
<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">30 / (3/5)</gadget>
<output>50</output>

<gadget id="calculator">50 - 48</gadget>
<output>2</output>

<result>2</result>