For this question, I understand how Greg got the answer by imagining that the number of incorrect questions is 4 from the start. I, on the other hand, did not do that method when I was solving and I originally just figured out how many points he got right to get at least 90% correct which is 108/120. And then I figured out how many wrong points there were which is 120-108 = 12 wrong points or less.
Since there were max 12 wrong points and for section 2 you can get -1 per wrong question so there couldve been 12 wrong questions. So i ended up choosing D.
Can someone help me to figure out why my method is wrong?
You were on the right track in the first paragraph, but from there on you seem to have got confused. For example,
“section 2 you can get -1 per wrong question so there couldve been 12 wrong questions” is not correct - try computing this explicitly and see what you get, and
you made no attempt to minimise the number of wrong answers (you seemed to have tried maximising instead).
12 questions wrong in section two would be -1\times 12 =-12 points. I understand how if i could’ve gotten 4 questions wrong if its in section 1 since -3\times4 = -12 points.
Not really. Let’s suppose you got 12 wrong and 18 correct in section 2. The number of points you got in that section would be
18 \times 2 - 12 \times 1 = 36 - 12 = 24
which is actually a loss of 36 points compared to if you got all questions right. The reason is that when you get something wrong, you don’t get the +2 you would get if you got it right instead.
Hm I see. I kind of understand what you are saying. Then without using Greg’s method of imagining that the answer is 4, how could I approach this using my original method of calculating 108/120 and finding out how many wrong questions equal to -12 points?
I went with the same strategy-
for a 90% score, the actual score should be - 108/120
now for section 1 : 1 incorrect answer leads you to -4 for every wrong question (-3 for incorrect answer and -1 for the score you could have got but would not be getting it now)
similarly, for section 2 : -3 (-1-2)
Section 3 : -4 (-2-2)
So score you lose for every incorrect answer in these sections are
S1 : (-4), S2 :(-3), S3 :(-4)
now it is not possible for there to be 1 question wrong from section 2 and others are wrong from section 1&3. due to ODD/Even Common sense.
therefore there are 2 possible cases-
case 1 - 3 questions are incorrect which leads to -4 in score
3 *(-4)=12
case 2 - 4 questions are incorrect which leads to -3 in score
4 *(-3)=12
Therefore, I think the answer should be not enough information.(as both 3 & 4 are possible).
Do let me know what you guys think?
Also where did you get this question, so that I can the particular video or quiz and understand if I missed something.
Think about how many points you really lose when you get something wrong from full points. For Section 1, you actually lose (-2 - 1) (i.e, 3) points for each wrong answer. In other words, if you have 29 correct and one wrong in section 1, you get 29\times2 - 1 = 57, a 3 points loss in essence.
yes you are right.
It is just that the final answer can 3 or 4 therefore I think it is not possible to confirm the answer with the present info.
Ideally the question should state something like “making the least number of mistakes”, etc.
Hi,
Sorry I stand corrected, I missed out “above” written in the question.
So score you lose for every incorrect answer in these sections are
S1 : (-4), S2 :(-3), S3 :(-4).
now the score should be greater than (>)108 meaning not including 108.
so the cases are
Case 1:
3 ques of (-3): 3*(-3)=-9 now -3 or -4 cannot come here as the number will exceed or be equal -12 (or 108).
Case 2:
2 ques of (-4) and 1 ques of (-3): 2*(-4)+1*(-3)=-11 anything else cannot come here as the number will exceed or be equal -12 (or 108).
So “above” is my something else.
Answer would be B. (3 is the only possible incorrect questions)
