Damn it! Exam! - Part 3

Algebra Level 2

Mehul and Nihar had a social studies exam of 20 marks. The marking scheme was : 2 marks for a correct answer ,-0.5 marks for a incorrect answer and 0 marks for not attempted questions. Mehul scored 50% marks and came to know that he had attempted 6 questions correctly. Nihar attempted the same no. of question as that of Mehul but he attempted 8 questions correctly. What is the score of Nihar?

The answer is 15.

1 solution

Chew-Seong Cheong
May 15, 2015

Mehul scored $50\%$ meaning that he had $10$ marks.
Since Mehul got $6$ questions correct meaning that he got $12$ marks from correct answer and deducted $2$ marks for answering $4$ question wrongly.
Therefore, Mehul had attempted $10$ questions. $6$ correctly and $4$ wrongly.
So, Nihar had also attempted $10$ questions and got $8$ correctly and $2$ wrongly, meaning he scored $8\times 2 - 2\times 0.5 = \boxed{15}$ marks.

I got the right answer, but didn't read the problem carefully enough. I thought it was asking for a percentage so I typed 75... 15/20=.75=75%. That annoys me a lot...

Well, here's my solution.

c= # correct w= # wrong i= # unanswered

2c- w/2 + 0i = Total marks

the exam is scored out of 20 marks so, for Mehul, (2c-w/2+0i)/20 = 50%

2c- w/2 +0i =10

It is given that Mehul answered 6 questions correctly, thus w must be 4.

If Nihar attempted the same number of questions, then w + c must be constant. w+c must be 10. If c increases by 2, from 6 to 8, then w must decrease by 2, from 4 to 2. For Nihar, c=8 and w=2. Nihar's total marks are 2c -w/2, or 2(8)- 2/2.

Nihar had 15 marks. Nihar had 75%.

Jared Jones - 6 years ago

You can't give a score in % in the question then ask for a score in marks without explicitly stating you want the mark score for your answer.

Nate Thönnesen - 5 years, 10 months ago

Damn it! Exam! - Part 3

The answer is 15.

1 solution

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