There are 20 girls in Class 1, accounting for 4/9 of the whole class. How many boys are there in Class 1?
六1班有女生20人，占全班人数的(4/9)，六1班有男生多少人？
<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">20 / (4/9)</gadget>
<output>45</output>

<gadget id="calculator">45 - 20</gadget>
<output>25</output>

<result>25</result>