There are 50 students in Class 1 of June. Girls account for 2/5 of the whole class. How many boys are there?
六1班有50人，女生占全班人数的(2/5)，男生有多少．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">50 * (3/5)</gadget>
<output>30</output>

<result>30</result>