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list of 15 numbers

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list of 15 numbers

by swapna » Mon Apr 19, 2010 6:15 pm
Are all of the numbers in a certain list of 15 numbers equal?

1. The sum of all numbers in the list is 60
2.The sum of any 3 numbers in the list is 12

ans: b

can some one exp??
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Source: — Data Sufficiency |
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by iamtensai » Mon Apr 19, 2010 7:13 pm
1. to get to the sum of 60, all 15 numbers could be equal (4), or they may vary (1, 4,4...4,3) => insufficient
2. this is sufficient on its own and it might help to break this down to a simpler case:
consider when you only have 4 numbers: a, b, c, d
if we know that the sum of any 3 numbers is 12, then we will get the equations
a+b+c =12
a+b +d =12
a +c+d=12
b+c+d=12

solve by subtracting any of the equations from each other and you will get a=b=c=d

the case with 15 numbers is just an extention with more variables.
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by eaakbari » Thu Apr 22, 2010 2:04 am
(2) If any 3 numbers of a set can give you the same same, the numbers of the set are bound to be equal. Suff
(1) Insuff
Answer is B
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