Data Sufficiency

What is the average (arithmetic mean) height of the n people in a certain group?

1. The average height of the n/3 tallest people in the group is 6 feet 2.5 inches, and the average height of the rest of the people in the group is 5 feet 10inches.
2. The sum of the heights of the n people is 178 feet 9 inches.

I feel ans should be A

Avg Heigh of n/3 people is 6 feet 2.5 inches
Avg height of rest of the people (2n/3) is 5 feet 10 inches

so Average height of n people is

((n/3* 6 feet 2.5 inches) + (2n/3 * 5 feet 10 inches) )/ n

Shudn't the answer be 'D', because one can find the average from the second option also, i.e.
178feet 9 inches/n = average height of n people.

Yup that's the answer. Thanks. I just made a stupid logic error.

ri2007 wrote:I feel ans should be A

Avg Heigh of n/3 people is 6 feet 2.5 inches
Avg height of rest of the people (2n/3) is 5 feet 10 inches

so Average height of n people is

((n/3* 6 feet 2.5 inches) + (2n/3 * 5 feet 10 inches) )/ n

bacardi_blast wrote:Shudn't the answer be 'D', because one can find the average from the second option also, i.e.
178feet 9 inches/n = average height of n people.

bacardi_blast

in the 2nd statement you know the total but you dont know the value of n so you cant get the avg.

In the first one you can cancel out n in the equation

Hi All,

Can someone please let me know, how do i decide when i should assume 'n' to be a variable and when it should represent a value?

For eg:
In the above example, i was assuming A to be ans because 178.9/n does not give me the absolute average interms of a number.

But looking at the solution by you guys, i feel there is a scope for discrepancy.

Any hints, as to how do i overcome this?

Thanks,
~ashley

ashleyd182 wrote:Hi All,

Can someone please let me know, how do i decide when i should assume 'n' to be a variable and when it should represent a value?

For eg:
In the above example, i was assuming A to be ans because 178.9/n does not give me the absolute average interms of a number.

But looking at the solution by you guys, i feel there is a scope for discrepancy.

Any hints, as to how do i overcome this?

Thanks,
~ashley

Hi ashley,
If question explicitly states "In term of N" in that case you can use N as a value..
in all other cases N has to be taken as a variable..

For example :- if this question wud hv been what is average of N people in terms of N then statement 2 wud have been sufficient...

Hope it helps