The average (arithmetic mean) of 10, 30, and 50 is 5 more : GMAT Problem Solving (PS)
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 17 Jan 2017, 10:38

### 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 (arithmetic mean) of 10, 30, and 50 is 5 more

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 36540
Followers: 7071

Kudos [?]: 93005 [0], given: 10541

The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

01 Oct 2012, 04:05
Expert's post
6
This post was
BOOKMARKED
00:00

Difficulty:

5% (low)

Question Stats:

80% (01:38) correct 20% (00:44) wrong based on 728 sessions

### HideShow timer Statistics

The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

Practice Questions
Question: 53
Page: 159
Difficulty: 600

GMAT Club is introducing a new project: The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

Each week we'll be posting several questions from The Official Guide for GMAT® Review, 13th Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.

We'll be glad if you participate in development of this project:
2. Please vote for the best solutions by pressing Kudos button;
3. Please vote for the questions themselves by pressing Kudos button;
4. Please share your views on difficulty level of the questions, so that we have most precise evaluation.

Thank you!
[Reveal] Spoiler: OA

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 36540
Followers: 7071

Kudos [?]: 93005 [1] , given: 10541

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

01 Oct 2012, 04:05
1
KUDOS
Expert's post
SOLUTION

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

The average of 10, 30, and 50 is $$\frac{10+30+50}{3}=30$$.

The average of 20, 40 and x must be 30-5=25, so the sum of these 3 numbers must be 3*25=75 --> 20+40+x=75 --> x=15.

_________________
Moderator
Joined: 01 Sep 2010
Posts: 3089
Followers: 783

Kudos [?]: 6515 [1] , given: 1007

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

01 Oct 2012, 04:29
1
KUDOS
The average of 10 30 50 is $$\frac{A = 10+30+50}{3}$$ $$= 30$$
The second Average must be 5 less : 25. Using common sense or back solve we can obtain the solution.

Starting with A because we need a small value in the difference.

So,$$\frac{A = 20+40+15}{3}$$ $$= 25$$

thanks
_________________
Director
Joined: 24 Aug 2009
Posts: 506
Schools: Harvard, Columbia, Stern, Booth, LSB,
Followers: 17

Kudos [?]: 674 [1] , given: 276

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

01 Oct 2012, 18:47
1
KUDOS
The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and
(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

Average of 10,30,50 = 30
Average of 20,40 & x = 25
so 60 + x = 75----> x = 15
_________________

If you like my Question/Explanation or the contribution, Kindly appreciate by pressing KUDOS.
Kudos always maximizes GMATCLUB worth
-Game Theory

If you have any question regarding my post, kindly pm me or else I won't be able to reply

Intern
Joined: 30 Aug 2011
Posts: 22
Location: United States
Schools: ISB '15
GMAT 1: 680 Q46 V37
WE: Project Management (Computer Software)
Followers: 0

Kudos [?]: 15 [3] , given: 17

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

03 Oct 2012, 23:47
3
KUDOS

Since 10, 30 and 50 are numbers in equally spaced sets, average is 30

Now 30 is 5 greater than 25 ....Thus average of 20, 40 and (x) is 25 ......This implies, sum of 3 numbers should be 75 to make the average = 25

Thus, answer is 15 = 75 - 20 - 40
Math Expert
Joined: 02 Sep 2009
Posts: 36540
Followers: 7071

Kudos [?]: 93005 [0], given: 10541

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

04 Oct 2012, 13:05
SOLUTION

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

The average of 10, 30, and 50 is $$\frac{10+30+50}{3}=30$$.

The average of 20, 40 and x must be 30-5=25, so the sum of these 3 numbers must be 3*25=75 --> 20+40+x=75 --> x=15.

Kudos points given to everyone with correct solution. Let me know if I missed someone.
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 13428
Followers: 575

Kudos [?]: 163 [0], given: 0

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

20 Aug 2014, 22:37
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.
_________________
Manager
Joined: 07 Apr 2014
Posts: 147
Followers: 1

Kudos [?]: 23 [0], given: 81

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

10 Sep 2014, 18:08
Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

Practice Questions
Question: 53
Page: 159
Difficulty: 600

GMAT Club is introducing a new project: The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

Each week we'll be posting several questions from The Official Guide for GMAT® Review, 13th Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.

We'll be glad if you participate in development of this project:
2. Please vote for the best solutions by pressing Kudos button;
3. Please vote for the questions themselves by pressing Kudos button;
4. Please share your views on difficulty level of the questions, so that we have most precise evaluation.

Thank you!

10+30+50 = 90

90/3=30.

so mean of 20+40+x should be 25...

25*3=75(total),

60+x=75

x=15.
SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1858
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Followers: 47

Kudos [?]: 1928 [1] , given: 193

The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

10 Sep 2014, 21:54
1
KUDOS
Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

Algebraic Method (Forming single equation for result)

$$\frac{10 + 30 + 50}{3} = \frac{20 + 40 + x}{3} + 5$$

x = 15

Shortcut (By observation) Method

10, 30, 50 are equally spaced; so average = 30

For the other set, required average would be 30 - 5 = 25

It means total = 75

Required number = 75 - (20+40) = 15
_________________

Kindly press "+1 Kudos" to appreciate

GMAT Club Legend
Joined: 09 Sep 2013
Posts: 13428
Followers: 575

Kudos [?]: 163 [0], given: 0

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

01 Oct 2015, 20:29
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.
_________________
Senior Manager
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 458
Followers: 22

Kudos [?]: 186 [0], given: 2

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

30 May 2016, 04:24
Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

Let’s first determine the average of 10, 30, and 50, using the average formula.

average = sum/quantity

average = (10+30+50)/3

average = 90/3

average = 30

We can now rephrase the question to ask: "30 is 5 more than the average of 20, 40, and what value?" Let’s label the missing value as n and create an equation.

30 = (20+40+n)/3 + 5

25 = (20+40+n)/3

75 = 60 + n

15 = n

_________________

Jeffrey Miller
Jeffrey Miller

Senior Manager
Joined: 18 Jan 2010
Posts: 257
Followers: 5

Kudos [?]: 87 [0], given: 9

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

30 May 2016, 05:15
[quote="Bunuel"]The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55
/quote]

avg of (10, 30, 50) = (10+30+50)/ 3 = 30.

Avg of next set = 25.

There are 3 nos. So sum of those 3 nos. = 25 * 3 = 75.
Third number = 75 - 20-40 = 15

BSchool Forum Moderator
Joined: 12 Aug 2015
Posts: 1889
Followers: 46

Kudos [?]: 355 [0], given: 448

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

17 Dec 2016, 16:30
Here is my solution to this one =>

Mean(1) = 30 (Notice that it is an AP series so the median will be the mean)

Mean(2)=$$\frac{60+x}{3}$$

As per question
$$30=\frac{60+x}{3} +5$$
Hence x=15
Hence A

_________________

Mock Test -1 (Integer Properties Basic Quiz) ---> http://gmatclub.com/forum/stonecold-s-mock-test-217160.html#p1676182

Mock Test -2 (Integer Properties Advanced Quiz) --->http://gmatclub.com/forum/stonecold-s-mock-test-217160.html#p1765951

Give me a hell yeah ...!!!!!

Manager
Joined: 25 Mar 2013
Posts: 196
Location: United States
Concentration: Entrepreneurship, Marketing
GPA: 3.5
Followers: 2

Kudos [?]: 21 [0], given: 87

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

### Show Tags

28 Dec 2016, 16:42
$$a1 : \frac{90}{3} = 30$$
a2: $$25 = \frac{60 + x}{3}$$
x = 15
A
_________________

I welcome analysis on my posts and kudo +1 if helpful. It helps me to improve my craft.Thank you

Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more   [#permalink] 28 Dec 2016, 16:42
Similar topics Replies Last post
Similar
Topics:
2 In a certain set the average (arithmetic mean) is known to be 30 and 6 13 Dec 2016, 06:40
The average (arithmetic mean) of 20, 40, and 60 is 5 more than the ave 6 31 May 2016, 01:35
What is the average (arithmetic mean) of all multiples of 10 2 13 Oct 2015, 10:10
3 The average (arithmetic mean) of 4 positive integers is 50. 4 21 Dec 2013, 03:31
3 The average (arithmetic mean) of the weight of 10 vehicles 5 23 Apr 2012, 04:19
Display posts from previous: Sort by