The ratio of the number of boys to the number of girls participating in the dance interest group is 1:5. After the transfer of 4 boys in the new semester, the ratio of the number of boys to the number of girls is 1:10. How many boys are there in the dance interest group?
参加舞蹈兴趣小组的男生人数和女生人数的比是1：5，新学期转走4名男生后，男生人数和女生人数的比是1：10，原来舞蹈兴趣小组有男生多少人．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/5) - (1/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">4 / (1/10)</gadget>
<output>40</output>

<gadget id="calculator">40 * (1/5)</gadget>
<output>8</output>

<result>8</result>