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Set A consists of a set of n consecutive integers. Is the sum of all t

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New post 12 Mar 2019, 22:49
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Set A consists of a set of n consecutive integers. Is the sum of all the integers in set A even?

(1) If -5 is added to set A, the set would become symmetric about 0

(2) If the largest integer of set A is removed, the sum of the remaining integers is even
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New post 14 Mar 2019, 10:05
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If a set is symmetric, its mean equals its median. Statement 1 tells us that by inserting "-5" in the set, we get a symmetric set with a median of 0, which thus has a mean of 0, and therefore a sum of 0. Since by inserting "-5" in the set we reduce the sum by 5, the original set must sum to 5, so its sum is odd, and the information is sufficient to give a "no" answer to the question. (I haven't even used the fact that the integers are consecutive, but another way to do this is to notice that the only set of consecutive integers that becomes symmetric around 0 when you insert "-5" is the set -4, -3, -2, -1, 0, 1, 2, 3, 4, 5).

Statement 2 tells us that the sum of all but one of the elements is even, but we don't know if the largest element is even or odd, so we have no way to tell if the sum of every element is even or odd. So the answer is A.
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Re: Set A consists of a set of n consecutive integers. Is the sum of all t  [#permalink]

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New post 24 Mar 2019, 10:32
mangamma wrote:
Set A consists of a set of n consecutive integers. Is the sum of all the integers in set A even?

(1) If -5 is added to set A, the set would become symmetric about 0

(2) If the largest integer of set A is removed, the sum of the remaining integers is even


#1
by symmetric it means that count of integers on both sides of 0 i.e + & -ve are equal
so
-5,-4,-3,-2,-1,0,1,2,3,4,5
so sum = 0
sufficient
#2
largest integer of set A is remove , sum is even
so we can have
-3,-2-1 ,0,1 so 1 is removed ; -6
or
-3,-2,-1,0,1,2,3,4,5 ,; 5 is removed ; sum is 4
or
-3,-2,-1,0,1,2,3,4; 4 is removed ; sum = 0
in sufficient
IMO A
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Re: Set A consists of a set of n consecutive integers. Is the sum of all t   [#permalink] 24 Mar 2019, 10:32
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