Mean and Sum

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Mean and Sum

by didieravoaka » Sat Apr 23, 2016 6:59 am
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Does someone can help on this one?

Thanks.

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by [email protected] » Sat Apr 23, 2016 10:15 am
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

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by OptimusPrep » Sun Apr 24, 2016 8:05 pm
didieravoaka wrote:Image

Does someone can help on this one?

Thanks.
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?