Tricky Wording

[GHong14]

What is the average height of n people in the group?

1. The average height of n/3 tallest people in the group is 6 feet and the rest average height is 5 feet.

2. The sum of n height is 190 feet.

I really doing understand the wording of statment 1. Anyone care to explain. The correct answer is A

[ksundar]

What is the average height of n people in the group?

1. The average height of n/3 tallest people in the group is 6 feet and the rest average height is 5 feet.

2. The sum of n height is 190 feet.

I really doing understand the wording of statment 1. Anyone care to explain. The correct answer is A

Statement 1 is sufficient. Ans will be 16/3 any number you substitute
Statement 2 is insufficient. Average of n height is 190/n. n is still an unknown.

So answer is A

[GHong14]

Can you please explain how you got 16/3? Is the question asking for how many people there are in the group. Or how many people are over 6 foot in the group

[Night reader]

What is the average height of n people in the group?

1. The average height of n/3 tallest people in the group is 6 feet and the rest average height is 5 feet.

2. The sum of n height is 190 feet.

I really doing understand the wording of statment 1. Anyone care to explain. The correct answer is A

Statement 1 is sufficient. Ans will be 16/3 any number you substitute
Statement 2 is insufficient. Average of n height is 190/n. n is still an unknown.

So answer is A

????

GHong14, read the solution below

Statement (1)

'The average height of n/3 tallest people in the group is 6 feet' - means, Average (s1) for n/3 is equal to 6 feet; the weighted average coefficient of this sample (n/3) within our general pool (n) is 1/3 - just remember for a moment

'... the rest average height is 5 feet' - means, Average (s2) for n-n/3 or 2n/3 is equal to 5 feet; the weighted average coefficient of this sample (2n/3) within our general pool (n) is 2/3 - remember this too

Now bring together Averages s1 and s2 and find the average height of pool/people (1/3) * 6 + (2/3) * 5 = 6/3 + 10/3 = 16/3

Statement (1) is sufficient since we find the average height of n people as 16/3 or 5 1/3

Statement (2)

'The sum of n height is 190 feet' - means, the sum of all (n) people heights is equal to 190 feet.

We need to find the average of n people height; average formula, S(average) = 190/n. We are missing n here.

Statement (2) is insufficient.

Select A.

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One of the things I always do on a DS question, is to identity if its a value question or a yes/no question. This question is a value question-hence we need to find a specific value.

In order to find the average height, we would need the sum of all the heights & the number of people. Answer choice which gives us the 2 pieces of information( or a relationship between the 2 variables) is sufficient. if not then it is insufficient.

stmt 1 gives us the avg height of n/3 people & avg height of remaining(2n/3) people. Hence, for finding the average, we can create the equation: (6n/3+5*2n/3)/n. We can cancel n from numerator and denominator & find out the avg weight. hence sufficient

stmt2 gives us the total weight but not the number of people n. Hence insufficient

[Testluv]

Hi,

if we know the concept of balanced average, we can do far less math to see that (1) is sufficient:

(1) tells us that a third of the people are 6 ft while two-thirds of the people are 5 ft. Because there are twice as many 5-footers, the grand average is twice as close to 5 than it is to 6...5 ft 4 in.

Another example:

For 3/4 of a math class, the average score on the midterm was 60 while the other 1/4's average was 40. What is the average of the entire class?

Well, since there are three times as many 60-scorers than 40-scorers, the average should be three times closer to 60 than it is to 40...55.

The less math you do in a DS question, the quicker you can solve it; NOT doing math is an important skill in DS.