There are 420 students in the sixth grade participating in the physical education standard test. Those who are excellent account for 80% of the total number of students, and the number of qualified students accounts for 5/28 of the number of excellent students.
六年级有学生420人参加体育达标测试，达到优秀的占总人数的80%，合格的人数占优秀人数的(5/28)，其余的均不合格，则不合格的学生有多少人？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">5 / 28</gadget>
<output>5/28 = around 0.178571</output>

<gadget id="calculator">(4/5) * (5/28)</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 - (4/5) - (1/7)</gadget>
<output>2/35 = around 0.057143</output>

<gadget id="calculator">420 * (2/35)</gadget>
<output>24</output>

<result>24</result>