A student is given a true - false exam with 10 questions. If he gets 8 or more correct answers he passes the exam. Given that he guesses at the answer to each question, what is the probability that he passes the exam ?

• To pass the exam one should have 8,9 or 10 correct answers
  
  There are 1024 ways to answer the questions 2^10 = 1024 ways.
  
  There are 10C8 ways to get 8 out of 10 correct
  10C8 = 10 x 9 / 2! = 45 ways
  
  There are 10C9 ways to get 9 out of 10 correct
  10C9 = 10 / 1! = 10 ways
  
  There are 10C10 ways to get 10 out 10 correct
  10C10 = 1 way
  
  45 + 10 + 1 = 56 good outcomes out of 1024 possible outcomes.
  
  56 / 1024 = 0.05469
  
  Answer:
  Approx. 5.47%
• 9 years agoHelpfull: Yes(44) No(2)
• For every question we have 2 options true and false.
  so for a question to be correct the probability is 1/2.
  possible answers are {8,9,10}
  so probability is (1/2^8)+(1/2^9)+(1/2^10)=7/2^10.
• 9 years agoHelpfull: Yes(2) No(2)
• can u tell me how to post questio.i want to post my tcs questions
  
• 9 years agoHelpfull: Yes(1) No(1)
• payel every question has two ways to be answered as either true or as false
  So as for one question there is 2 ways
  So for 10 questions 2X2X2X2X2X2X2X2X2X2 = 2^10 ways
  
• 9 years agoHelpfull: Yes(1) No(1)
• 7/2^7
  10c8+10c9+10c10/2^10
  
• 9 years agoHelpfull: Yes(1) No(0)
• the no of ways he can answer 10 questions is= 2^10
  the no of ways of getting 8 of them right =2^8
  the probability of passing=2^8/2^10 =1/4
  
• 9 years agoHelpfull: Yes(0) No(8)
• 32^10,,,total 2^10 and passinf prob is 0nly 3,if he ans 8,9 or 10 correcrt soooo,ans
  
• 9 years agoHelpfull: Yes(0) No(0)
• the no of ways he can answer 10 questions = 2^10
  the no of ways of passing the test(by obtaining either 8 or 9 or 10 correct)= 2^3
  The probability of passing = 2^3/2^10 = 1/2^7 = 1/128
• 9 years agoHelpfull: Yes(0) No(1)
• X=he passes exam if he get 8,9or 10 marks
  then P(x)=3/10=.3
• 9 years agoHelpfull: Yes(0) No(1)
• kartika cant get your logic.total possible outcome=2^10??why?pls explain the logic.
• 9 years agoHelpfull: Yes(0) No(0)