There are 45 students in the second class of the fifth year, including 20 girls. What percentage of the whole class are boys?
五年二班有45人，其中女生有20人，男生人数占全班人数的几分之几？
<gadget id="calculator">45 - 20</gadget>
<output>25</output>

<gadget id="calculator">25 / 45</gadget>
<output>5/9 = around 0.555556</output>

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