Question

one boy asked the question about fraction of 16/17 but by mistake he answered devide it16/17 and now answer is more than33/340 from the right answer​

Answer 1

Answer:

Step-by-step explanation:

Exam consists of 10 multiple choice questions.Whre out of 4 option one is correct and 3 are wrong.

Candidate get 3 marks fot every right question and −1 mark for every incorrect answer.

If the candidate attempts all of 10 questions, then from the set 15,16,17,18,19,20,.he can only achieve the score of 18, by marking 7 coorect options and 3 incorrect option.

If he attempts any more or less than 7 questions, then the score becomes out of the range of the set. Only if he does 7 correct questions, he can score 18 out of given set.  

Now we know to get a score of 18, the candidate needs to correct only 7 questions out of 10, it means he will mark 3 questions incorrectly.  

So number of possible combinations to get a score of 18 consists the number of ways he can chose the 7 correct answer multiplied by number of way he can incorrect the 3 questions.

Hence number of possible distinct combinations will be 10  

C  

7

​  

 

​  

.(3)  

3

 

Where (3)  

3

 are the number of possible way he can incorrectly mark the 3 questions, as every question has 3 incorrect choice out of 4. So for 3 questions, it will 3.3.3=(3)  

3

 

Hence total number of distinct possible combinations will be 10  

C  

7

​  

 

​  

.(3)  

3

=120×27=3240

So correct answer is C.

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