Students in the sixth grade take the test and are required to answer five questions, and it is stipulated that those who answer 3 or more questions correctly are qualified for the test. The test results are: 81% of the first question is correct, 91% of the second question is correct, 85% of the third question is correct, 79% of the fourth question is correct, and 74% of the fifth question is correct. What is the pass rate index?
六年级同学参加测试，要求回答五道试题，并且规定凡答对3道或3道以上的为测试合格．测试结果是：答对第一题的有81%，答对第二题的有91%，答对第三题的有85%，答对第四题的有79%，答对第五题的有74%，那合格率指数是多少？
<gadget id="calculator">500 - 410</gadget>
<output>90</output>

<gadget id="calculator">90 / 3</gadget>
<output>30</output>

<gadget id="calculator">100 - 30</gadget>
<output>70</output>

<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

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

<result>7/10 = around 0.7</result>