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14 Jan 2015, 02:50
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
95%
(hard)
Question Stats:
36% (01:48) correct
64%
(01:41)
wrong
based on 269
sessions
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Not Attempted Yet
For a certain set of n numbers, where n > 2, is the average (arithmetic mean) equal to the median?
(1) The n numbers are positive, consecutive even integers.
(2) The average of the n numbers is equal to the average of the largest and smallest numbers in the set.
Kudos for a correct solution.
(1) The n numbers are positive, consecutive even integers.
(2) The average of the n numbers is equal to the average of the largest and smallest numbers in the set.
Kudos for a correct solution.
19 Jan 2015, 19:32
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Hi anupamadw,
Many DS questions include some type of "test" of your thoroughness - in other words, "do you 'see' more than just the 'obvious' answer?"
Here, your understanding of the concepts is strong when you're focused on positive integers. But what happens when the integers are NOT positive.....?
You properly assessed Fact 1, so I won't rehash any of that work here. Notice how Fact 1 "restricted" you to POSITIVE, CONSECUTIVE, EVEN integers? NONE of those restrictions exist in Fact 2...
Consider this set of numbers: {-1, 0, 6, 6, 9}
The average of the group = 4
The average of the smallest and biggest = 4
The median of the group = 6
Here, the average is NOT = to the median, so the answer to the question is NO.
You already have some examples that show that the answer could be YES.
Fact 2 is INSUFFICIENT.
To be fair, most DS questions don't require that you do too much to "break" a pattern in the possible answers, but you have to be ready to consider more than just the obvious. Here, the "obvious" was "positive integers and no duplicates."
GMAT assassins aren't born, they're made,
Rich
Many DS questions include some type of "test" of your thoroughness - in other words, "do you 'see' more than just the 'obvious' answer?"
Here, your understanding of the concepts is strong when you're focused on positive integers. But what happens when the integers are NOT positive.....?
You properly assessed Fact 1, so I won't rehash any of that work here. Notice how Fact 1 "restricted" you to POSITIVE, CONSECUTIVE, EVEN integers? NONE of those restrictions exist in Fact 2...
Consider this set of numbers: {-1, 0, 6, 6, 9}
The average of the group = 4
The average of the smallest and biggest = 4
The median of the group = 6
Here, the average is NOT = to the median, so the answer to the question is NO.
You already have some examples that show that the answer could be YES.
Fact 2 is INSUFFICIENT.
To be fair, most DS questions don't require that you do too much to "break" a pattern in the possible answers, but you have to be ready to consider more than just the obvious. Here, the "obvious" was "positive integers and no duplicates."
GMAT assassins aren't born, they're made,
Rich
General Discussion
15 Jan 2015, 06:11
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Bunuel
stat1. The n numbers are positive, consecutive even integers.
For consecutive integers, arithmatic mean = Median
e.g. 2 4 6 8 am=5 and median = avg of middle 2 numbers = (4+6)/2 =5 --> am = median
e.g 2 4 6 8 10 am=30/5=6 and median = 6
suff
stat2
The average of the n numbers is equal to the average of the largest and smallest numbers in the set.
avg=(a1+an) / 2 --> This is also property of consecutive integers.
and for all consecutive integers --> am=median
suff
IMO : D
Pls correct me if I am wrong, Many Thanks
