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Manager
Joined: 19 Aug 2009
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26 Aug 2009, 03:23
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Q.
In a class 25% of the students were absent for an exam. 30% failed by 20 marks and 10% just passed because of grace marks of 5. Find the average score of the class if the remaining students scored an average of 60 marks and the pass marks are 33.

1. 37.266
2. 37.6
3. 37.8
4. 36.93
5. 37.5

Pretty easy question but answer given is 37.6 ( considering 75% students when calculating average...i understand 25% are absent...but when average of class is asked shouldnt 100% be included--- pls solve this confusion?)

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Senior Manager
Joined: 18 Aug 2009
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Schools: UT at Austin, Indiana State University, UC at Berkeley
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26 Aug 2009, 03:56
Can not understand the wording of the problem. Pls help
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Manager
Joined: 27 May 2009
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26 Aug 2009, 04:09
thr's somthing rong here?
Director
Joined: 01 Apr 2008
Posts: 814
Name: Ronak Amin
Schools: IIM Lucknow (IPMX) - Class of 2014

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26 Aug 2009, 12:06
Ans should be 27.7 !! Anything missing?
Manager
Joined: 25 Aug 2009
Posts: 162

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26 Aug 2009, 13:44
Question seems to be incomplete. What is the source of this question?
Manager
Joined: 28 Jul 2009
Posts: 116
Location: India
Schools: NUS, NTU, SMU, AGSM, Melbourne School of Business

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27 Aug 2009, 05:01
Something is wrong here. What is the source?
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Manager
Joined: 13 Jan 2009
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27 Aug 2009, 05:37
Definitely something is wrong!
Intern
Joined: 30 Jun 2009
Posts: 48

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27 Aug 2009, 06:12
Economist wrote:
Ans should be 27.7 !! Anything missing?

Hi buddy,
asuming that question is ok, how did you get to your 27.7?
I have a totally different nbr

Assuming it is a class of 200 students.
50 were absent, and 150 were at the exam.
30% failed by 20 marks => means 45 students scored 13
10% just passed with a 5mark grant => means 15 students scored 28
the rest scored 60 => 90 students

avg = {(45x13)+(15x28)+(90x60)}/200 = 32.025

am I doing something wrong here?

Director
Joined: 01 Apr 2008
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Name: Ronak Amin
Schools: IIM Lucknow (IPMX) - Class of 2014

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27 Aug 2009, 06:42
defoue wrote:
Economist wrote:
Ans should be 27.7 !! Anything missing?

Hi buddy,
asuming that question is ok, how did you get to your 27.7?
I have a totally different nbr

Assuming it is a class of 200 students.
50 were absent, and 150 were at the exam.
30% failed by 20 marks => means 45 students scored 13
10% just passed with a 5mark grant => means 15 students scored 28
the rest scored 60 => 90 students

avg = {(45x13)+(15x28)+(90x60)}/200 = 32.025

am I doing something wrong here?

Actually it is a poorly worded question. I took 30% of overall students, you have taken 30% of passed students and so on...that is why we are getting different answers. Logically yes, absent students are to be discounted but the question does not specify anything. It is also possible that 30% of overall failed
Manager
Joined: 10 Jul 2009
Posts: 145

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27 Aug 2009, 07:03
What is the source for this question?
Manager
Joined: 27 May 2009
Posts: 237

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27 Aug 2009, 07:07
1
guess the ques is right ..IMO B

say 100 students are in class

75 appeared for test. 33 is passing mark

30 students got 13 marks each and failed by 20 marks - their total marks = 390

10 got 28 marks each and just passed by 5 grace - their total marks = 280 (excluding grace marks)

remaining 35 got 60 on average - their total marks = 2100

total marks secured by all 75 who appeared in test = 390+280+2100 = 2770

avg marks = 2770/75 = 36.93

-->note that if grace marks are included for 10 just passed students then

their total = 330

final total = 2820

avg marks = 2820/75 = 37.6

So it means grace marks have to be included
Manager
Joined: 10 Aug 2009
Posts: 129

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27 Aug 2009, 09:22
1
rohansherry wrote:
guess the ques is right ..IMO B

say 100 students are in class

75 appeared for test. 33 is passing mark

30 students got 13 marks each and failed by 20 marks - their total marks = 390

10 got 28 marks each and just passed by 5 grace - their total marks = 280 (excluding grace marks)

remaining 35 got 60 on average - their total marks = 2100

total marks secured by all 75 who appeared in test = 390+280+2100 = 2770

avg marks = 2770/75 = 36.93

-->note that if grace marks are included for 10 just passed students then

their total = 330

final total = 2820

avg marks = 2820/75 = 37.6

So it means grace marks have to be included

I comletely agree with this solution. No one says that absent students fail the course and should be given 0. But it is a tricky one. Kudo for you.
If you do not include 25% that were abscent you get the following:
40%X13+13.33%X28+46.66%X60=36.93

However, answer is D. They say "remaining"...so overlap is not possible
Manager
Joined: 13 Jan 2009
Posts: 162

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28 Aug 2009, 02:43
rohansherry wrote:
guess the ques is right ..IMO B

say 100 students are in class

75 appeared for test. 33 is passing mark

30 students got 13 marks each and failed by 20 marks - their total marks = 390

10 got 28 marks each and just passed by 5 grace - their total marks = 280 (excluding grace marks)

remaining 35 got 60 on average - their total marks = 2100

total marks secured by all 75 who appeared in test = 390+280+2100 = 2770

avg marks = 2770/75 = 36.93

-->note that if grace marks are included for 10 just passed students then

their total = 330

final total = 2820

avg marks = 2820/75 = 37.6

So it means grace marks have to be included

Why did you assume that all 10 students got 28? If the grace mark is 5, I understand that they could get min 28 marks. Is it possible the student got 30 marks and passed due to grace mark is 5? Correct me if i'm wrong
Intern
Joined: 09 Aug 2009
Posts: 46

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28 Aug 2009, 03:44
defoue wrote:
Economist wrote:
Ans should be 27.7 !! Anything missing?

Hi buddy,
asuming that question is ok, how did you get to your 27.7?
I have a totally different nbr

Assuming it is a class of 200 students.
50 were absent, and 150 were at the exam.
30% failed by 20 marks => means 45 students scored 13
10% just passed with a 5mark grant => means 15 students scored 28
the rest scored 60 => 90 students

avg = {(45x13)+(15x28)+(90x60)}/200 = 32.025

am I doing something wrong here?

I guess you need to include the grace marks also(anyway this marks also comes into the account).
Assuming total 200 students
30% = 45*13 = 585
10% = 15*33 = 495
60% = 90*60 = 5400
=32.2

/Prabu
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Re: Percentage/ average &nbs [#permalink] 17 Sep 2017, 22:20
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