There is a class in Experimental Primary School, with 45 students in the class, and the number of students who are good students accounts for 2/5 of the whole class. If there are more students who are good students, the students who are good students account for the whole class (4/9).
实验小学有一个班，全班45人，三好学生人数占全班的(2/5)，再增加多少个三好学生，三好学生就是全班的(4/9)．
<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

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

<gadget id="calculator">(4/9) - (2/5)</gadget>
<output>2/45 = around 0.044444</output>

<gadget id="calculator">45 * (2/45)</gadget>
<output>2</output>

<result>2</result>