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Re: DS: Are all the numbers in a certain list integers/ [#permalink]
29 Nov 2009, 10:52

B. (1) says nothing. (2) the list incluses a,b,c...n (n=20) numbers. a+b=b+c=> a=c. a+c=c+d=> a=d Similarly, a=b=c=....=n. Hence all the numbers are equal. B. _________________

Re: Are all the numbers in a certain list of 20 numbers equal? [#permalink]
11 Jul 2013, 21:10

1

This post received KUDOS

Mountain14 wrote:

GMAT TIGER wrote:

Are all the numbers in a certain list of 20 numbers equal?

1) The sum of any 2 numbers in the list is an integer. 2) The sum of any 2 numbers in the list is 10.

Hi All,

Though its an old post, but I am unable to understand why B is the answer....

From Stm#2 - ( 2, 4,5,5,6....)

4+6 = 10 5+5=10 ...

So, how can be prove the numbers are equal??

If the list is as you say ( 2, 4,5,5,6....), then the sum of ANY two numbers wont be 10.. eg :2+4 = 6, 2+6 = 8, 2+5=7, 4+4 = 8, 6+6 = 12 _________________

Did you find this post helpful?... Please let me know through the Kudos button.

Re: Are all the numbers in a certain list of 20 numbers equal? [#permalink]
11 Jul 2013, 22:18

1

This post received KUDOS

Expert's post

Mountain14 wrote:

GMAT TIGER wrote:

Are all the numbers in a certain list of 20 numbers equal?

1) The sum of any 2 numbers in the list is an integer. 2) The sum of any 2 numbers in the list is 10.

Hi All,

Though its an old post, but I am unable to understand why B is the answer....

From Stm#2 - ( 2, 4,5,5,6....)

4+6 = 10 5+5=10 ...

So, how can be prove the numbers are equal??

Are all the numbers in a certain list of 20 numbers equal?

(1) The sum of any 2 numbers in the list is an integer. Clearly insufficient. For example, consider {0.5, 0.5, 0.5, ..., 0.5, 1.5} or {1, 1, 1, ...}

(2) The sum of any 2 numbers in the list is 10. Since the sum of ANY 2 numbers is 10, then ALL numbers must equal to 10/2=5, because if not all the numbers equal to 5, then we could pick certain set of 2 numbers so that their sum is not 10. Sufficient.