Mean and Sum
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Hi didieravoaka,
This question can be solved by TESTing VALUES and some basic conceptual knowledge.
We're told that List K has 7 numbers. We're asked if the average of the list is NEGATIVE. This is a YES/NO question.
1) Four of the seven numbers in List K are negative.
IF the numbers are...
{1, 1, 1, 1, 0, 0, 0} then the average is negative and the answer to the question is YES.
{1, 1, 1, 1, 10, 10, 10} then the average is positive and the answer to the question is NO.
Fact 1 is INSUFFICIENT.
2) The sum of the seven numbers in List K is negative.
From this Fact, we know that the SUM is NEGATIVE, so taking the average of the list (re: dividing by 7) will still leave us with a NEGATIVE result. Thus, the answer to the question is ALWAYS YES.
Fact 2 is SUFFICIENT.
Final Answer: B
GMAT assassins aren't born, they're made,
Rich
This question can be solved by TESTing VALUES and some basic conceptual knowledge.
We're told that List K has 7 numbers. We're asked if the average of the list is NEGATIVE. This is a YES/NO question.
1) Four of the seven numbers in List K are negative.
IF the numbers are...
{1, 1, 1, 1, 0, 0, 0} then the average is negative and the answer to the question is YES.
{1, 1, 1, 1, 10, 10, 10} then the average is positive and the answer to the question is NO.
Fact 1 is INSUFFICIENT.
2) The sum of the seven numbers in List K is negative.
From this Fact, we know that the SUM is NEGATIVE, so taking the average of the list (re: dividing by 7) will still leave us with a NEGATIVE result. Thus, the answer to the question is ALWAYS YES.
Fact 2 is SUFFICIENT.
Final Answer: B
GMAT assassins aren't born, they're made,
Rich
 OptimusPrep
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Given: List K contains 7 numbers
Required: Is the average negative?
Statement 1: 4 of the 7 numbers are negative.
We cannot conclude anything from this as the values are not known
Case 1: K = {1, 2, 3, 4, 0, 1, 2} Here the average would be negative
Case 2: L = {1, 2, 3, 4, 100, 1000, 10000} Here the average would be positive
INSUFFICIENT
Statement 2: Sum of 7 numbers in K is negative
Average = Sum / # of elements
In this case, since the sum is negative, hence the average will be negative too
SUFFICIENT
Correct Option: B
What problem were you facing?