It is currently 21 Oct 2017, 02:16

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# The average score of x number of exams is y. When an additional exam

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 41891

Kudos [?]: 129072 [0], given: 12194

The average score of x number of exams is y. When an additional exam [#permalink]

### Show Tags

08 Oct 2014, 14:23
Expert's post
3
This post was
BOOKMARKED
00:00

Difficulty:

65% (hard)

Question Stats:

63% (01:54) correct 37% (03:03) wrong based on 135 sessions

### HideShow timer Statistics

Tough and Tricky questions: Statistics

The average score of x number of exams is y. When an additional exam of score z is added in, does the average score of the exams increase by 50%?

(1) 3x = y
(2) 2z - 3y = xy
[Reveal] Spoiler: OA

_________________

Kudos [?]: 129072 [0], given: 12194

Manager
Joined: 22 Jan 2014
Posts: 141

Kudos [?]: 74 [0], given: 145

WE: Project Management (Computer Hardware)
Re: The average score of x number of exams is y. When an additional exam [#permalink]

### Show Tags

08 Oct 2014, 23:00
Bunuel wrote:

Tough and Tricky questions: Statistics

The average score of x number of exams is y. When an additional exam of score z is added in, does the average score of the exams increase by 50%?

(1) 3x = y
(2) 2z - 3y = xy

B.

The questions can be mathematically represented as:

(xy+z)/(x+1) = 1.5y --- (A)

1) 3x=y
clearly insufficient as we have no info about z.

2) 2z-3y=xy
this is nothing but the simplified form of equation (A)
sufficient.
_________________

Illegitimi non carborundum.

Kudos [?]: 74 [0], given: 145

VP
Joined: 14 Nov 2016
Posts: 1161

Kudos [?]: 1183 [0], given: 415

Location: Malaysia
The average of a set of x exam scores is y. When an additional exam of [#permalink]

### Show Tags

23 Mar 2017, 23:55
The average of a set of x exam scores is y. When an additional exam of score z is added to the set, does the average score of the exams increase by 50%?

(1) $$3 x = y$$
(2) $$2 z – 3 y = xy$$
_________________

"Be challenged at EVERY MOMENT."

“Strength doesn’t come from what you can do. It comes from overcoming the things you once thought you couldn’t.”

"Each stage of the journey is crucial to attaining new heights of knowledge."

Kudos [?]: 1183 [0], given: 415

Intern
Joined: 12 Oct 2016
Posts: 2

Kudos [?]: [0], given: 170

GMAT 1: 660 Q47 V35
Re: The average of a set of x exam scores is y. When an additional exam of [#permalink]

### Show Tags

24 Mar 2017, 00:16
Sum of the exam scores = xy
When new score z is introduced, sum is xy+z
Avg =( xy+z)/x+1
Question is asking if (xy+z)/x+1 = 150% of y
On solving, we get xy = 2z-3y, which is given in statement b
Hence B.

Kudos [?]: [0], given: 170

Math Expert
Joined: 02 Sep 2009
Posts: 41891

Kudos [?]: 129072 [0], given: 12194

Re: The average score of x number of exams is y. When an additional exam [#permalink]

### Show Tags

24 Mar 2017, 01:06
ziyuen wrote:
The average of a set of x exam scores is y. When an additional exam of score z is added to the set, does the average score of the exams increase by 50%?

(1) $$3 x = y$$
(2) $$2 z – 3 y = xy$$

Merging topics. Please refer to the discussion above.
_________________

Kudos [?]: 129072 [0], given: 12194

Math Forum Moderator
Joined: 13 Apr 2015
Posts: 1504

Kudos [?]: 1113 [0], given: 884

Location: India
Concentration: Strategy, General Management
WE: Information Technology (Consulting)
Re: The average score of x number of exams is y. When an additional exam [#permalink]

### Show Tags

24 Mar 2017, 02:01
1
This post was
BOOKMARKED
Alternate method:

Let number of exams = x = 10
average = y = 50

Question: Is (500 + z)/11 = 75?

St1: x = 3y --> Clearly insufficient as we do not know anything about z.

St2: z = (xy + 3y)/2 = (500 + 150)/2
We know the value of z.
Sufficient.

Kudos [?]: 1113 [0], given: 884

Director
Joined: 12 Nov 2016
Posts: 784

Kudos [?]: 35 [0], given: 164

Re: The average score of x number of exams is y. When an additional exam [#permalink]

### Show Tags

11 Sep 2017, 05:31
Bunuel wrote:

Tough and Tricky questions: Statistics

The average score of x number of exams is y. When an additional exam of score z is added in, does the average score of the exams increase by 50%?

(1) 3x = y
(2) 2z - 3y = xy

St 1

St 2

Holds true for all scenarios for example

x=3 ,y=4

x=5, y=6

B

Kudos [?]: 35 [0], given: 164

Re: The average score of x number of exams is y. When an additional exam   [#permalink] 11 Sep 2017, 05:31
Display posts from previous: Sort by