An aerobics competition was held in the sixth grade of a certain elementary school, and the number of girls participating in the competition was 28 more than that of boys. As a result, all boys won prizes, while 25% of girls did not win prizes. The total number of boys and girls who won prizes was 42. It is also known that the ratio of the number of people participating in the competition to the number of the whole grade is 2:5. How many students are there in sixth grade in this school?
某小学六年级举行健美操比赛，参加比赛的女生比男生多28人．结果男生全部获奖，女生则有25%的人未获奖，男女生获奖总人数为42人．又已知参加比赛的人数与全年级人数的比是2：5．该校六年级一共有多少人？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">28 * (1/4)</gadget>
<output>7</output>

<gadget id="calculator">42 - 28</gadget>
<output>14</output>

<gadget id="calculator">7 + 14</gadget>
<output>21</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 + (3/4)</gadget>
<output>7/4 = around 1.75</output>

<gadget id="calculator">21 / (7/4)</gadget>
<output>12</output>

<gadget id="calculator">12 + 28 + 12</gadget>
<output>52</output>

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

<gadget id="calculator">52 / (2/5)</gadget>
<output>130</output>

<result>130</result>