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AM doubt

by rahul26 » Thu May 07, 2009 3:25 pm
The average (arithmetic mean) of a list of numbers is what percent of the sum of the numbers?
(1) There are 8 numbers in the list.
(2) The sum of the numbers in the list is 100.

I thought the ans was E which doesn't seem to be the correct OA?
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Re: AM doubt

by Ian Stewart » Thu May 07, 2009 5:23 pm
rahul26 wrote:The average (arithmetic mean) of a list of numbers is what percent of the sum of the numbers?
(1) There are 8 numbers in the list.
(2) The sum of the numbers in the list is 100.

I thought the ans was E which doesn't seem to be the correct OA?
avg = sum/n

From S1, n=8, we have:

avg = sum/8

If the average is 1/8th of the sum, it's equal to 12.5% of the sum, and Statement 1 is sufficient.

________

I've ignored a small technicality above; as worded, the question does not exclude the possibility that the sum of the numbers is zero. Of course, if the sum of the numbers is zero, the question doesn't make any sense (it becomes 'zero is what percent of zero?') and if the above were a real GMAT question, the question would definitely include the restriction that all of the numbers in the list are positive.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

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Re: AM doubt

by aj5105 » Thu May 14, 2009 10:04 pm
That's cool Ian.
Ian Stewart wrote:
rahul26 wrote:The average (arithmetic mean) of a list of numbers is what percent of the sum of the numbers?
(1) There are 8 numbers in the list.
(2) The sum of the numbers in the list is 100.

I thought the ans was E which doesn't seem to be the correct OA?
avg = sum/n

From S1, n=8, we have:

avg = sum/8

If the average is 1/8th of the sum, it's equal to 12.5% of the sum, and Statement 1 is sufficient.

________

I've ignored a small technicality above; as worded, the question does not exclude the possibility that the sum of the numbers is zero. Of course, if the sum of the numbers is zero, the question doesn't make any sense (it becomes 'zero is what percent of zero?') and if the above were a real GMAT question, the question would definitely include the restriction that all of the numbers in the list are positive.
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