The ratio of boys to all students in a school is 4:9, how much more girls than boys.
一所学校男生与全校学生的比是4：9，女生比男生人数多多少．
<gadget id="calculator">9 - 4 - 4</gadget>
<output>1</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>