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Source: — Data Sufficiency |

by Tryingmybest » Sat Nov 22, 2008 1:26 pm
To me its E

From both statements we dont know what n is?

Meaning both statements will hold good for any value of n leaving us no definitive way to determine the average.

Please correct me if I am wrong.
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by cramya » Sat Nov 22, 2008 2:21 pm
It's A)(weighted average concept)

Stmt I)

n/3(6ft2 1/2inches) + 2n/3*5ft 10 inches / N = avg

n cancels out and therefore we can find avearge

SUFF

Stmt II

sum = 178 ft 9 inches

DONT KNOW N CANT FIND AVERAGE
INSUFF

A)
Last edited by cramya on Sat Nov 22, 2008 6:17 pm, edited 1 time in total.
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by Tryingmybest » Sat Nov 22, 2008 4:36 pm
Thanks Cramya!!
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by lunarpower » Mon Nov 24, 2008 5:28 am
Looking at statement (2) first, we see that it is not sufficient, because the average (arithmetic mean) of a group of numbers is defined as (sum of data) / (# of data points). With statement (2), we only have the numerator of this expression (the # of people in the group is unknown), so we can't figure out the average.

Looking at statement (1) alone, we can set up the average as follows:
Average = (sum of data points) / (# of data points)
= [(n/3)(74.5) + (2n/3)(70)] / (n) <-- note that I used inches here, so I won't have to write in more fractions than necessary (trying to write fractions on this forum is not fun)
= [(1/3)(74.5) + (2/3)(70)] / (n)
There's no need to simplify further, because the 'n' is gone: you get one number. Therefore, this statement is sufficient.

Answer = A

Note that, if you have the averages of all the FRACTIONS or PERCENTAGES of a group, then you'll be able to calculate the overall average of the group. This is a worthwhile fact to memorize for the data sufficiency problems.
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