The number of fifth grade is 25% of the whole school, then the rest of the grade is the whole school ((())/(())), the fifth grade boys are the whole class (3/5), then the number of boys is the whole school ．
五年级人数是全校人数的25%，那么其余年级是全校人数的((())/(()))，五年级男生是全班人数的(3/5)，那么男生是全校人数的多少．
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

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

<gadget id="calculator">(1/4) * (3/5)</gadget>
<output>3/20 = around 0.15</output>

<result>3/20 = around 0.15</result>