BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

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

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Tue Feb 05, 2019 6:33 am
AAPL wrote:Manhattan Prep

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?

A. 24
B. 25
C. 26
D. 27
E. 28OA
D
If the average age is 25, we can write: (sum of all 3 ages)/3 = 25
This means, the sum of all 3 ages = 75

If the median is 24, then we can express the ages in ascending order as follows: __ , 24, __

Since the sum of the ages is 75, we can MINIMIZE the age of the oldest girl by MAXIMIZING the age of the youngest girl.
Well, the youngest girl cannot be older than the median age (24), but the "youngest" girl can also be 24 (so there are 2 youngest sisters)
We get: 24, 24, __

Finally, since the sum of all 3 ages = 75, the oldest girl must be 27 years old.

Answer: D

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Legendary Member
Posts: 2499
Joined: Sun Oct 29, 2017 2:04 pm
Followed by:6 members

by swerve » Tue Feb 05, 2019 9:55 am
a + b + c = 75

Given -

a + 24+ c = 75

Now, a + c = 51

Now comes the fun part, so check using options...

Here C is the oldest sister, and we need to minimize c by maximizing a.

A. If c = 24 , a = 27 (not Possible as a > c)
B. If c = 25 , a = 26 (not Possible as a > c)
C. If c = 26 , a = 25 (not Possible as a > b < c)
D. If c = 27 , a = 24 (possible as a ≤ b < c)
E. If c = 28 , a = 23 (Possible as but now, this is not the minimum value c can take)

Therefore, the correct answer must be D
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 8086
Joined: Sat Apr 25, 2015 10:56 am
Location: Los Angeles, CA
Thanked: 43 times
Followed by:29 members

by Scott@TargetTestPrep » Wed Feb 06, 2019 6:34 pm
AAPL wrote:Manhattan Prep

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?

A. 24
B. 25
C. 26
D. 27
E. 28

OA D
Since 3 sisters have an average age of 25 years, the sum of their ages is 75.

To minimize the age of the oldest sister, we want to maximize the ages of the two youngest sisters. Since the median is 24, the two youngest sisters could both be 24 years old.

Thus, the minimum possible age of the oldest sister is 75 - (24 + 24) = 75 - 48 = 27.

Answer: D

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage
Top
Post new topic Post Reply
• Page 1 of 1