GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 16 Oct 2019, 08:35

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# The average (arithmetic mean) score of b quizzes for a group of studen

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 58380
The average (arithmetic mean) score of b quizzes for a group of studen  [#permalink]

### Show Tags

08 Jan 2018, 23:59
00:00

Difficulty:

35% (medium)

Question Stats:

70% (01:51) correct 30% (02:12) wrong based on 56 sessions

### HideShow timer Statistics

The average (arithmetic mean) score of b quizzes for a group of students is 6.4. When one quiz score is discarded, the average of the remaining quiz scores becomes 4.8. What is the discarded quiz score?

A. 1.6b ­­­­­­+ 24
B. 1.6b – 4.8
C. 1.6b + 4.8
D. 6.4b – 24
E. 6.4b +4.8

_________________
Senior PS Moderator
Joined: 26 Feb 2016
Posts: 3341
Location: India
GPA: 3.12
The average (arithmetic mean) score of b quizzes for a group of studen  [#permalink]

### Show Tags

09 Jan 2018, 00:28
1
Bunuel wrote:
The average (arithmetic mean) score of b quizzes for a group of students is 6.4. When one quiz score is discarded, the average of the remaining quiz scores becomes 4.8. What is the discarded quiz score?

A. 1.6b ­­­­­­+ 24
B. 1.6b – 4.8
C. 1.6b + 4.8
D. 6.4b – 24
E. 6.4b +4.8

Let the total score of b quizzes be x.

From the question stem, we have $$\frac{x}{b}$$ = 6.4 => x = 6.4b -> (1)

When including the discarded score, $$\frac{x-A}{b-1}$$ = 4.8 where A is the discarded score.
Substituting the value of x from equation (1), we get $$\frac{6.4b-A}{b-1} = 4.8$$

Simplifying, we get $$6.4b - A = 4.8(b-1) = 4.8b - 4.8$$

Therefore, the discarded score A = 6.4b - (4.8b - 4.8) = 1.6b + 4.8(Option C)
_________________
You've got what it takes, but it will take everything you've got
Current Student
Joined: 18 Aug 2016
Posts: 609
Concentration: Strategy, Technology
GMAT 1: 630 Q47 V29
GMAT 2: 740 Q51 V38
Re: The average (arithmetic mean) score of b quizzes for a group of studen  [#permalink]

### Show Tags

09 Jan 2018, 00:29
Bunuel wrote:
The average (arithmetic mean) score of b quizzes for a group of students is 6.4. When one quiz score is discarded, the average of the remaining quiz scores becomes 4.8. What is the discarded quiz score?

A. 1.6b ­­­­­­+ 24
B. 1.6b – 4.8
C. 1.6b + 4.8
D. 6.4b – 24
E. 6.4b +4.8

$$(6.4b - x)/ (b-1) = 4.8$$
x = 1.6b + 4.8
C
_________________
We must try to achieve the best within us

Thanks
Luckisnoexcuse
Intern
Joined: 15 Aug 2017
Posts: 12
Re: The average (arithmetic mean) score of b quizzes for a group of studen  [#permalink]

### Show Tags

10 Jan 2018, 01:58
4
(6.4b-X)/b-1 =4.8
X= 1.6+4.8
so, C
Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4781
Location: India
GPA: 3.5
Re: The average (arithmetic mean) score of b quizzes for a group of studen  [#permalink]

### Show Tags

10 Jan 2018, 08:45
Bunuel wrote:
The average (arithmetic mean) score of b quizzes for a group of students is 6.4. When one quiz score is discarded, the average of the remaining quiz scores becomes 4.8. What is the discarded quiz score?

A. 1.6b ­­­­­­+ 24
B. 1.6b – 4.8
C. 1.6b + 4.8
D. 6.4b – 24
E. 6.4b +4.8

$$\frac{6.4b - d}{( b -1 )} = 4.8$$

$$6.4b - d = 4.8b - 4.8$$

Or, $$1.6b + 4.8 = d$$

So, the discarded quiz score is 1.6b + 4.8 , answer will be (C)
_________________
Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )
Intern
Joined: 24 Nov 2016
Posts: 30
Re: The average (arithmetic mean) score of b quizzes for a group of studen  [#permalink]

### Show Tags

10 Jan 2018, 11:26
average = total sum / total q

1) 6.4 = x/b = 6.4b-x
2) 4.8 = x/b-1 = 4.8b - 4.8 - x

6.4b-x=4.8b-4.8-x
1.6b+4.8
Senior SC Moderator
Joined: 22 May 2016
Posts: 3543
The average (arithmetic mean) score of b quizzes for a group of studen  [#permalink]

### Show Tags

10 Jan 2018, 11:45
1
Bunuel wrote:
The average (arithmetic mean) score of b quizzes for a group of students is 6.4. When one quiz score is discarded, the average of the remaining quiz scores becomes 4.8. What is the discarded quiz score?

A. 1.6b ­­­­­­+ 24
B. 1.6b – 4.8
C. 1.6b + 4.8
D. 6.4b – 24
E. 6.4b +4.8

A*n = S

First set of scores
A = 6.4, n = b
Sum, S = 6.4b

A = 4.8, n = (b - 1)
Sum, S = 4.8(b - 1) = (4.8b - 4.8)

The difference in sums is the discarded score:
6.4b - (4.8b - 4.8) =
6.4b - 4.8b + 4.8 =
1.6b + 4.8

Algebra is faster, but if you're really stuck, assign values.

(Average, A) * (number of terms,n) = Sum, S

Let b = 2

Then the sum for the first set of scores is A*n = S: (6.4 * 2) = 12.8
One score is removed. Number, n, of scores is now (2-1)= 1
Sum for second set of scores:(4.8 * 1) = 4.8

The score that was removed is
(Sum1 - Sum 2) = (12.8 - 4.8) = 8

With b = 2, find the answer that yields 8
Discard A and E (they are huge)
Discard B and D (with a little mental math, it's clear they're negative)

C. 1.6b + 4.8
(1.6)(2) + 4.8 = (3.2 + 4.8) = 8 MATCH

_________________
SC Butler has resumed! Get two SC questions to practice, whose links you can find by date, here.

Choose life.
Non-Human User
Joined: 09 Sep 2013
Posts: 13203
Re: The average (arithmetic mean) score of b quizzes for a group of studen  [#permalink]

### Show Tags

20 Jan 2019, 12:00
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: The average (arithmetic mean) score of b quizzes for a group of studen   [#permalink] 20 Jan 2019, 12:00
Display posts from previous: Sort by