Students in Class 1, Grade 6 held a speech contest. When a boy gave a speech on the stage, the ratio of the number of boys and girls sitting below was 5:3. When a girl gave a speech (boys returned to their seats), due to special needs , need another girl to come to the stage to do auxiliary work, at this time the ratio of boys and girls present here is 2:1, how many girls are there in this class?
六年级1班的同学进行演讲比赛，当一位男生在台上演讲时，底下在座的男女生人数之比为5：3，当一位女生上台演讲时(男生回到座位)，由于特殊需要，需要另一位女生上台作辅助工作，此时底下在座的男女生的比为2：1，这个班有女生多少人？
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">5 / 3</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">2 - (5/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">5 / (1/3)</gadget>
<output>15</output>

<result>15</result>