Find all School-related info fast with the new School-Specific MBA Forum

It is currently 30 Aug 2014, 10:33

Close

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Three sisters have an average (arithmetic mean) age of 25 ye

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
User avatar
Joined: 12 Dec 2012
Posts: 163
Location: Poland
Followers: 4

Kudos [?]: 90 [0], given: 67

Three sisters have an average (arithmetic mean) age of 25 ye [#permalink] New post 14 Jan 2013, 05:16
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

67% (01:54) correct 33% (01:06) wrong based on 52 sessions
This post is about a doubtful assumption, perhaps an error in the book, which however doesn't influence the answer to the original question.
Source: Manhattan Advanced GMAT Quant
Try-It 7-13:

Three sisters have an average (arithmetic mean) age of 25 years and a median age of 24 years. What is the minimum possible age, in years, of the oldest sister?

f = age of the first sister, etc.
M = Median = 24
m = mean

\frac{f+s+t}{3}=25=m

M=s=24

f+s=51

My assumption:
The problem says about the oldest sister, so I assumed that:

f≤s<t

In case the younger sisters were twins. The book explains: The youngest sister must be less than or equal to 24 years old. Agreed.

However, the book also assumes that:

s≤t:

Of course, the oldest sister must be at least as old as the middle sister (...) Not agreed. (Further implications concerning M=24 that turn the ≤ into the < possibility are correct.)

My thinking is: If there is one sister that is the oldest, she must not be the same age as the younger sister(s). Hypothetically, she could be 9 months older and still born in the same year, but I think it is impossible from the medical point of view. Or the sisters could be a step sisters, etc. Nevertheless, this situation is purely hypothetical and - even if the point was to mislead the thinker - in my opinion this is a bit too much, because the very natural assumption for expression of an age is it be an integer.

Moreover, if there were a hypothetical sets:

A={24,25,25},
OR
B={25,25,25},

none of the elements in each set were the greatest (oldest), because "the greatest" is an expression inherently relative to some other objects.

Disputably, in the A'={24,25} we could point 25 as "the greatest", because it's the greatest within the set, even though inside the set it is only "the greater" element, because there is only one other element to be relatively smaller (24).

If you have a one brother, you never say "I am his oldest brother" (unless you're joking).
Instead, you will say: "I am his older brother.". Ain't right?

And if you have two siblings, you will say: "I am the oldest one (of us three).", won't you?


OAs:
(A) 24
(B) 25
(C) 26
(D) 27
(E) 28
[Reveal] Spoiler: OA

_________________

If I answered your question with this post, use the motivating power of kudos!

Kaplan Promo CodeKnewton GMAT Discount CodesManhattan GMAT Discount Codes
Manager
Manager
avatar
Joined: 18 Oct 2011
Posts: 92
Location: United States
Concentration: Entrepreneurship, Marketing
GMAT Date: 01-30-2013
GPA: 3.3
Followers: 2

Kudos [?]: 24 [0], given: 0

Re: Three sisters have an average (arithmetic mean) age of 25 ye [#permalink] New post 15 Jan 2013, 08:32
This question is fairly simple. Note that in the question stem they do not say that each sister has a different age..meaning two could have the same age. If we have a median of 24 that means the middle sister is 24. If we have a mean of 25 that means that the total age of all 3 sisters is 75. If you take out the middle sisters age from the total you get 51...the youngest and oldest sisters must combine for 51 years.
The first answer choice that makes sense is 27 years for the oldest sister leaving the middle and youngest to be 24.
Manager
Manager
User avatar
Joined: 12 Dec 2012
Posts: 163
Location: Poland
Followers: 4

Kudos [?]: 90 [0], given: 67

Re: Three sisters have an average (arithmetic mean) age of 25 ye [#permalink] New post 15 Jan 2013, 08:59
Dear sambam,
Quote:
This post is about a doubtful assumption, perhaps an error in the book, which however doesn't influence the answer to the original question.

Solving the problem as such is not the purpose of my post.
I would be glad if you've read the whole story before answering ;).
_________________

If I answered your question with this post, use the motivating power of kudos!

Re: Three sisters have an average (arithmetic mean) age of 25 ye   [#permalink] 15 Jan 2013, 08:59
    Similar topics Author Replies Last post
Similar
Topics:
1 Experts publish their posts in the topic Three straight metal rods have an average (arithmetic mean) DelSingh 4 27 Feb 2013, 21:23
34 Experts publish their posts in the topic Seven pieces of rope have an average (arithmetic mean) lengt Walkabout 18 20 Dec 2012, 06:46
8 Experts publish their posts in the topic Three boxes of supplies have an average (arithmetic mean) sameerdrana 8 05 Dec 2010, 13:17
Three pieces of wire have an average (arithmetic mean) chenhong1224 2 10 Oct 2008, 10:23
3 boxes of supplies have an average (arithmetic mean) weight uphillclimb 8 02 Nov 2006, 19:08
Display posts from previous: Sort by

Three sisters have an average (arithmetic mean) age of 25 ye

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.