Classes A, B, and C have equal numbers of students. The number of boys in class A is equal to the number of girls in class B. The number of girls in class C is equal to the number of boys in class B. The number of boys in class C accounts for 2/5 of the total number of boys in the three classes. What percentage of the total number of boys in the three classes?
甲、乙、丙三个班人数相等，甲班男生人数和乙班女生人数相等，丙班女生人数和乙班男生人数相等．丙班男生人数占三个班男生总数的(2/5)，三个班中男生占全部人数的几分之几？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5) - (2/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5) + (2/5) + (1/5)</gadget>
<output>9/5 = around 1.8</output>

<gadget id="calculator">1 / (9/5)</gadget>
<output>5/9 = around 0.555556</output>

<result>5/9 = around 0.555556</result>