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You can miss all of them, if you like! You will fail miserably, but you did not say you wanted to pass!
Three 15 = 100% 1.5 = 10% 3 = 20% as a miss is 100% - 80% = 20%
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90 x 20% = 90 x 0.20 = 18 If you miss 18 questions out of 90, you will get an 80% on the test.
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You can miss all of them, if you like! You will fail miserably, but you did not say you wanted to pass!
Three 15 = 100% 1.5 = 10% 3 = 20% as a miss is 100% - 80% = 20%
22
90 x 20% = 90 x 0.20 = 18 If you miss 18 questions out of 90, you will get an 80% on the test.
You didn't provide enough information ! HOWEVER - assuming you meant you need 70%, and each question is 1 mark, then you need to answer 14 questions correctly.
Provided that all the ones that you do not miss are correct, then 30% of 90 = 90*30/100 = 27.
To get at least 64% you can miss at most 100 - 64 % = 36 % Percent means "out of 100" 36 % of 56 = 36/100 x 56 = 20.16 → Can miss 20 questions.
100%-80%=20%10*.2=2Therefore you missed 2 questions.
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