There are 30 members in the school's track and field team, and at least one of any 10 of them is a fifth-grade student, then how many fifth-grade students does the track and field team have?
学校田径队有30名队员，其中任意10人中至少有一名是五年级的学生，则这个田径队至少有多少名五年级学生．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">30 - 9</gadget>
<output>21</output>

<result>21</result>