Z is a set of positive numbers. The median of Z is greater than the mean of Z. Which of the following must be true?
I. At least 50% of the numbers in Z are smaller than the median.
II. Less than 50% of the numbers in Z are greater than the median.
III. The median of Z is greater than the average of the largest and smallest numbers in Z.
A. I only
B. II only
C. III only
D. I and III only
E. None of the above
OA E
Source: https://gmat.economist.com/btg?gsrc=btg
Z is a set of positive numbers. The median of Z is greater
This topic has expert replies
-
- Moderator
- Posts: 7187
- Joined: Thu Sep 07, 2017 4:43 pm
- Followed by:23 members
Timer
00:00
Your Answer
A
B
C
D
E
Global Stats
GMAT/MBA Expert
- Jay@ManhattanReview
- GMAT Instructor
- Posts: 3008
- Joined: Mon Aug 22, 2016 6:19 am
- Location: Grand Central / New York
- Thanked: 470 times
- Followed by:34 members
Since this is a roman numeral question and each of the three statements are independent of each other, we must think of Set Z such that the statements are challenged.BTGmoderatorDC wrote:Z is a set of positive numbers. The median of Z is greater than the mean of Z. Which of the following must be true?
I. At least 50% of the numbers in Z are smaller than the median.
II. Less than 50% of the numbers in Z are greater than the median.
III. The median of Z is greater than the average of the largest and smallest numbers in Z.
A. I only
B. II only
C. III only
D. I and III only
E. None of the above
OA E
Source: Economist GMAT
Let's see each statement one by one.
I. At least 50% of the numbers in Z are smaller than the median.
Say Z : {0, 2, 2, 4, 6, 6, 6}
Median = 4; Mean = 26/7 = 3.7...; we see that Median (4) > Mean (3.7), so this is a valid set.
The numbers smaller than Median (4) are 0, 2, and 2; there are 3 out of 7 numbers (3/7 * 100% < 50%) smaller than Median.
Statement I must not be true.
II. Less than 50% of the numbers in Z are greater than the median.
Say Z : {0, 1, 1, 3, 3, 3}
Median = (1 + 3)/2 = 2; Mean = 11/6 = 1.8...; we see that Median (2) > Mean (1.8), so this is a valid set.
The numbers greater than Median (2) are 3, 3, and 3; there are 3 out of 6 numbers (3/6 * 100% = 50%) greater than Median.
Statement II must not be true.
III. The median of Z is greater than the average of the largest and smallest numbers in Z.
Say Z : {0, 1, 1, 3, 3, 3}
Median = (1 + 3)/2 = 2; Mean = 11/6 = 1.8...; we see that Median (2) > Mean (1.8)
The the average of the largest and smallest numbers = (0 + 3)/2 = 2 = Median (2)
Statement III must not be true.
The correct answer: E
Hope this helps!
-Jay
_________________
Manhattan Review GRE Prep
Locations: GRE Classes Los Angeles | GMAT Prep Course Singapore | GRE Prep Orlando | SAT Prep Courses Toronto | and many more...
Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.