Grade 6 students sign up to participate in the mathematics interest group. The number of students who participate is 1/3 of the total number of students in grade 6. Later, 24 more students participate. At this time, the ratio of students who participated to those who did not participate is 3:4. How many people are there in the sixth grade?
六年级学生报名参加数学兴趣小组，参加的同学是六年级总人数的(1/3)，后来再多有24人参加，这时参加的同学与未参加的人数的比是3：4．六年级一共有多少人？
<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(3/7) - (1/3)</gadget>
<output>2/21 = around 0.095238</output>

<gadget id="calculator">24 / (2/21)</gadget>
<output>252</output>

<result>252</result>