There are 49 students in a class, and the ratio of boys to girls is 3:4. How many girls are there in this class?
一个班级有学生49人，男生人数与女生的比是3：4．这个班级有女生多少人？
<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">49 * (4/7)</gadget>
<output>28</output>

<result>28</result>