A question has 7 options. If he chooses correct answer he can get one mark. If he chooses wrong option he looses one mark. If he chooses randomly he gets zero marks. Any way he identifies 2 options and eliminates them. If he chooses randomly how many marks can he gain?

• probability to choose correct option=1/7 and associated marks is 1;
  probability to choose incorrect option=6/7 and associated marks is x(let);
  total marks={(1/7)*1}+{(6/7)*x}=0, i.e. x=-1/6;
  now 2 options are eliminated,
  so,now,
  {(1/5)*1}+{(4/5)*(-1/6)}=1/15;
  ans is 1/15.
  
  
  
• 13 years agoHelpfull: Yes(56) No(1)
• probability to choose correct answer is 1/7 and he get 1 marks for right answer
  probability to choose wrong answer is 6/7 and he loose 1 marks for wrong answer.
  
  Then
  (1/7)*1+(6/7)*-1=0 according to question
  which is invalid
  so the associated marks for wrong answer is not one it must be some unknown which can be find by the following
  Let the marks for wrong be X
  (1/7)*1+(6/7)*-X=0 according to question
  then x=-1/6
  
  After that he eliminated 2 incorrect options
  So
  probability to choose correct answer is 1/5
  and wrong answer is 4/5
  So his score={(1/5)*1}+{(4/5)*(-1/6)}
  =(1/5)+(-2/15)
  =1/15
  then x=-1/6
  
• 13 years agoHelpfull: Yes(4) No(0)
• the answer should be zero marks.
• 13 years agoHelpfull: Yes(2) No(3)
• i hope answer is 1........one question .....so max mark is 1 only....."If he chooses randomly how many marks can he gain"......how many marks can he gain is asked ....which means only if he choose correct option he gains....so answer is 1...
• 13 years agoHelpfull: Yes(1) No(2)
• (1/7)*6+(6/7)*x=0...x=-1
  (1/2)*6+(1/2)*(-1)=2.5
  ans is 2.5
• 13 years agoHelpfull: Yes(0) No(19)
• 0 or 1??? the problem is wrong.. ANS: Data insufficient...
  
  We can calculate probability we cant predict...
• 13 years agoHelpfull: Yes(0) No(1)
• ans is 1/5
  2 option are eliminated it means this option are incorrect
  now the correct option is out of 5 so if we choose randomly then 1/5 is the probability of an correct ans.
  
• 13 years agoHelpfull: Yes(0) No(0)
• ans should be zero marks.
• 13 years agoHelpfull: Yes(0) No(0)