There are 12 boys and 18 girls in Class 5 (1). How many boys account for the whole class?
五(一)班有男生12人，女生18人，男生人数占全班人数的几分之几？
<gadget id="calculator">12 + 18</gadget>
<output>30</output>

<gadget id="calculator">12 / 30</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>