Sixth grade students participate in voluntary labor, 30% of the whole grade will pick up garbage, and the rest will be divided into two groups according to the ratio of 2:5, and the group with a larger number will clean the railings. It is known that the number of people cleaning the railings is 28 more than those picking up rubbish. How many people in the sixth grade participate in voluntary labor?
六年级同学参加义务劳动，全年级人数的30%去捡垃圾，剩下的按2：5分成两组，其中人数较多的一组去擦栏杆．已知擦栏杆的人数比捡垃圾的多28人．六年级有多少人参加义务劳动？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">2 + 5</gadget>
<output>7</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(7/10) * (5/7)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) - (3/10)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">28 / (1/5)</gadget>
<output>140</output>

<result>140</result>