From "boys in a certain class account for (8/15)" of the whole class, it can be drawn: the number of the whole class * how many = the number of girls.
从"某班男生占全班人数的(8/15)"，可得出：全班人数*多少=女生人数．
<gadget id="calculator">8 / 15</gadget>
<output>8/15 = around 0.533333</output>

<gadget id="calculator">1 - (8/15)</gadget>
<output>7/15 = around 0.466667</output>

<result>7/15 = around 0.466667</result>