In a factory, 75% of the employees worked full time in the first quarter, 80% worked full time in the second quarter, 90% worked full time in the third quarter, and 95% worked full time in the fourth quarter. At least what percentage of the total number of employees in the factory are those who are fully present throughout the year?
某工厂第一季度有75%的人出全勤，第二季度有80%的人出全勤，第三季度有90%的人出全勤，第四季度有95%的人出全勤．全年全勤的人数至少占全厂职工总人数的百分之几？
<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">95 / 100</gadget>
<output>19/20 = around 0.95</output>

<gadget id="calculator">1 - (19/20)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/4) + (1/5) + (1/10) + (1/20)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>