| View previous topic :: View next topic |
| Author |
Message |
dandillion
Just gettin' started!
Joined: 26 Jul 2008
Posts: 9
Thanks given: 2
Thanked 0 times in 0 posts
|
 Posted: Sat Jul 26, 2008 3:44 pm Post subject: sets |
 |
|
Set A contains 20 numbers and set B contains 40 numbers. Is the range of Set B greater than 45?
(1) The range of Set A and Set B combined exceeds 50.
(2) The range of Set B is greater than the range of Set A.
Thank you. |
|
| Back to top |
|
 |
|
|
lunarpower
GMAT Instructor
Joined: 03 Mar 2008
Posts: 504
Thanks given: 0
Thanked 63 times in 61 posts
GMAT Score: 800
|
| Posted: Sat Jul 26, 2008 8:58 pm Post subject: |
|
|
first off, it doesn't really matter how many numbers are in the sets, because the range of the sets is what matters.
before looking at the statements, think about the possibilities for the individual sets:
* there's no minimum range necessary for either set; in fact, the individual sets can even have a range of zero, and still produce as large a combined range as you want.
for instance, set A could consist of twenty copies of the number 0, and set B could consist of forty copies of the number 100. in this case, each of the sets has a range of 0, but the combined range is 100.
* there's also no maximum range necessary, especially because there are no upper bounds imposed on the range of anything in the problem.
therefore, even if you combine the two statements:
* the range of set B could be really small. for instance, if set A is twenty 0's, and set B is twenty 99's and twenty 100's, then both conditions are satisfied, but the range of set B is only 1.
* the range of set B could also be huge. for instance, set A could range from 0-100, and set B could range from 100-1000. in that case, the range of set B is 900.
answer = e
_________________
ron purewal
instructor, mgmat
Learn more about me |
|
| Back to top |
|
|
|
augusto
Rising GMAT Star
Joined: 22 Jun 2008
Posts: 48
Thanks given: 12
Thanked 2 times in 2 posts
Location: UK
Test Date: 30/9/2008
Target GMAT Score: 720
|
| Posted: Sun Jul 27, 2008 12:18 am Post subject: |
|
|
Hi Guys,
I might be really wrong, but can you have duplicate elements in a set?
| Quote: | Definition 1 A set is a collection of distinct objects.
The objects can be real, physical things, or abstract, mathematical things.
The number of such objects can be finite or infinite. The only important
thing is that the objects be distinct, i.e., uniquely identifiable. |
(taken from http://www.ces.clemson.edu/~mjs/courses/misc/settheory.pdf)
But anyway I think the correct answer is E, because with both stems you can find scenarios where the range of B is greater than 45 and less than 45. |
|
| Back to top |
|
|
lunarpower
GMAT Instructor
Joined: 03 Mar 2008
Posts: 504
Thanks given: 0
Thanked 63 times in 61 posts
GMAT Score: 800
|
| Posted: Sun Jul 27, 2008 1:01 am Post subject: |
|
|
| augusto wrote: | Hi Guys,
I might be really wrong, but can you have duplicate elements in a set?
| Quote: | Definition 1 A set is a collection of distinct objects.
The objects can be real, physical things, or abstract, mathematical things.
The number of such objects can be finite or infinite. The only important
thing is that the objects be distinct, i.e., uniquely identifiable. |
(taken from http://www.ces.clemson.edu/~mjs/courses/misc/settheory.pdf)
But anyway I think the correct answer is E, because with both stems you can find scenarios where the range of B is greater than 45 and less than 45. |
yeah, you're right: even if the numbers in the sets are required to be distinct, the answer is still e.
if set A = integers 1-20, set B = integers 21-60, then answer = "no"
if set A = evens 2-40, set B = evens 42-120, then answer = "yes"
answer = e
--
in any case, yes, the formal mathematical definition of a set requires that its members be distinct. but i can guarantee you that you will not have to know that in order to get questions right on the gmat; there's just no way they'd require that degree of esoteric mathematical knowledge, unless they explicitly included the word "distinct" in their problem statements.
this is one of the dangers of using unsourced problems: they may require knowledge that the gmat doesn't actually test, or, in extreme situations, they may even use terminology in ways that contravene the rules followed by the gmat itself. only use problems from trusted sources!
also, i'll have to go back and look, but i could swear up and down that i've seen at least one official problem containing something like "the set {2, 3, 3, 4, 4, x, y}", which would mean that the gmat technically allows repeated members in "sets".
one more thing: there's a certain amount of ambiguity inherent in this topic anyway, because, in common statistical parlance, a "data set" is definitely allowed to have repeat values.
_________________
ron purewal
instructor, mgmat
Learn more about me |
|
| Back to top |
|
|
kris610
Really wants to Beat The GMAT!
Joined: 09 Mar 2007
Posts: 135
Thanks given: 0
Thanked 3 times in 3 posts
|
| Posted: Sun Jul 27, 2008 3:07 pm Post subject: |
|
|
| I agree that the data sets can contain duplicates. If not for duplicates, the concept of 'Mode' wouldn't be there in Statistics, right? On the GMAT, for a statistics question, I believe we can use examples of sets with duplicates unless the question explicitly indicates the elements of the set are unique. |
|
| Back to top |
|
|
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum
|
|
"GMAT" and other GMAC™ trademarks are registered trademarks of the Graduate Management Admission Council™. The Graduate Management Admission Council™ does not endorse, nor is it affiliated in any way with the owner or any content on this website. The opinions expressed here are solely those of the author or those of the members of this website. Copyright © 2008 BTG Test Prep, LLC. Powered by phpBB © 2001, 2005 phpBB Group.
|
|
