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On a true-false test of 100 items, every question that is a multiple of 4 is true, and all others are false. If a student marks every item that is a multiple of 3 false and all others true, how many of the 100 items will be correctly answered?

 Jul 25, 2020
 #1
avatar+26903 
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Every multiple 3x4 will be marked false   but they are true    so that will be 8 marked incorrectly  (12  24  36 48 60 72 84 96

  all of the other multiples of 4  (25 of them) will be marked as true minus the 8 above

    17 /25   will be correct 

 

edited:     sorry...i misread the question

17 of 25 will be correct for the multiples of 4

there are 75 other questions that have 'false' as an answer

      33 multiple of 3 will be marked false which is a correct answer EXCEPT for the 8 above

            33 - 8 = 25 will be correctly marked

 

25 + 17  out of 100 will be correct   42/100     ( I think !    Confusing  cheeky )

 Jul 25, 2020
edited by ElectricPavlov  Jul 25, 2020
 #2
avatar+83 
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It's correct :) thanks so much!

Swim2433  Jul 25, 2020
edited by Swim2433  Jul 26, 2020

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