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

 It is currently 17 Oct 2019, 21:27

### 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
Your Progress

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

# When 52-year old Jane joined a group of professionals

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
Director
Status: Manager
Joined: 27 Oct 2018
Posts: 676
Location: Egypt
Concentration: Strategy, International Business
GPA: 3.67
WE: Pharmaceuticals (Health Care)
When 52-year old Jane joined a group of professionals  [#permalink]

### Show Tags

26 Dec 2018, 10:57
00:00

Difficulty:

75% (hard)

Question Stats:

41% (02:38) correct 59% (02:25) wrong based on 22 sessions

### HideShow timer Statistics

When 52-year old Jane joined a group of professionals, the average (arithmetic mean) age of the group increased by ten percent. If the average age of the group before Jane joined was 26 years, how many professionals are there in the group now?

A) 9

B) 10

C) 11

D) 12

E) 13

_________________
Thanks for Kudos
Manager
Joined: 17 Mar 2015
Posts: 86
Re: When 52-year old Jane joined a group of professionals  [#permalink]

### Show Tags

26 Dec 2018, 13:08
2
Mahmoudfawzy83 wrote:
When 52-year old Jane joined a group of professionals, the average (arithmetic mean) age of the group increased by ten percent. If the average age of the group before Jane joined was 26 years, how many professionals are there in the group now?

A) 9

B) 10

C) 11

D) 12

E) 13

X = ORIGINAL SUM
N = ORIGINAL NUMBER

26 = X/N
X = 26N

After new member addition

26*1.1 = (X + 52)/(N+1)
Put X = 26N and solve for N
N=9

Now 9+1= 10 members

Please give Kudos!!!!!!!!!!!!!
Manhattan Prep Instructor
Joined: 04 Dec 2015
Posts: 832
GMAT 1: 790 Q51 V49
GRE 1: Q170 V170
Re: When 52-year old Jane joined a group of professionals  [#permalink]

### Show Tags

26 Dec 2018, 18:20
Mahmoudfawzy83 wrote:
When 52-year old Jane joined a group of professionals, the average (arithmetic mean) age of the group increased by ten percent. If the average age of the group before Jane joined was 26 years, how many professionals are there in the group now?

A) 9

B) 10

C) 11

D) 12

E) 13

You can treat this as a weighted averages problem!

You're averaging one 52-year-old (Jane), and an unknown number of 26-year-olds. (It doesn't matter that they might all have different ages; what we care about is that their average age is 26.)

The result is an average that's 10% higher than 26. So, the new average is 1.1(26), which equals 28.6.

Here's what we have:

professionals: 26 -------- average: 28.6 ---------------------------------------------- Jane: 52

Start by finding how far each group is from the average. The 26-year-olds are 2.6 years below the average, while Jane is 52-28.6 = 23.4 years above the average. That's a ratio of 2.6:23.4, or 26:234, or 1:9.

Since Jane's age is 9 times further from the average than everyone else's, there must be 9 times as many other people. So, there were 9 people in the group before Jane arrived, and now there are 10.
_________________

Chelsey Cooley | Manhattan Prep | Seattle and Online

My latest GMAT blog posts | Suggestions for blog articles are always welcome!
Re: When 52-year old Jane joined a group of professionals   [#permalink] 26 Dec 2018, 18:20
Display posts from previous: Sort by

# When 52-year old Jane joined a group of professionals

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne