The ratio of the number of girls to boys in Class 1, Grade 9 is 4:5, how much less girls than boys.
九年级一班女生和男生人数比是4：5，女生比男生少多少．
<gadget id="calculator">5 - 4</gadget>
<output>1</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>