During the sixth grade mathematics interest group activities, 60% of the students who participated were those who did not participate. Later, 30 people participated. At this time, only 2/3 of the students participated (2/3). How many people are there in the sixth grade?
六年级数学兴趣小组活动时，参加的同学是未参加的60%，后来又有30人参加，这时参加的同学是未参加的(2/3)，六年级一共有多少人？
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

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

<gadget id="calculator">3 + 5</gadget>
<output>8</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">(2/5) - (3/8)</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">30 / (1/40)</gadget>
<output>1_200</output>

<result>1_200</result>