Answers

2014-07-18T18:39:42+05:30
Firstly find the total marks i.e. equal to 180X4=720
now , he hav scored 450 marks so marks deducted=720-450=270
now ,these for each wrong or unattempted question marks deducted is 5 as 4 of the question and 1 of the negative marking,so no.of questions wrong or unattempted is 270/5 = 54
therefore no. of answers correct =180-54=126
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2014-07-18T18:50:18+05:30
Let, no. of correctly done questions = x
  no of wrong answered question & un-attempted questions = y 
a/q,  total questions = 180=x+y---------------eqn(1)
          4x-y=450----eqn(2)
    eqn(1)+eqn(2)
   5x=630 
     x = 126
    y=180-126=54
therefore 126 questions correctly done.
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