Data Sufficiency

gdk800 wrote: Q2) If 11 consecutive integers are listed from least to most, which is the mean of the 11 digits?
a. Average of the first 9 digits is 7
b. Average of last 9 digits is 9

OA is D.

gdk800 wrote:Q1) In sequence an = an-1 + k, where 2 ≤ n ≤ 15 and k is a nonzero constant. How many of the terms in the sequence are greater than 10?
a. a1 = 24
b. a8 = 10

If 11 consecutive integers are listed in increasing order, what is the average (arithmetic mean) of these integers?

(1) The average of the first 9 integers is 7
(2) The average of the last 9 integers is 9

beat_gmat_09 wrote:B) a8=10, if k+ve all values from a9-a15 will be > 10, thus number of terms > 10 is 15-9 = 6
if k-ve, a7, a6,a5 ....a2 will all be <10 and a9,a10,a11.....a15 will be > 10, hence number of terms > 10 = 15-9 =6
In either case number of terms is 6. Sufficient.

gdk800 wrote:A sincere Thanks to all members for such detailed explanations.

shovan85 wrote:

gdk800 wrote: Q2) If 11 consecutive integers are listed from least to most, which is the mean of the 11 digits?
a. Average of the first 9 digits is 7
b. Average of last 9 digits is 9

OA is D.

Shovan, Is There any difference between Digits and integers,
According to me digits are from 0 to 9 , and integer can be any number that can be represented on the number line,

Now Question is the means of 11 digits , I thought that there is a series like 71 72 73 74 75 76 ..........

and we want to determine the mean of first 11 digits of the series

I) statement

The series i able to determine was 93 94 95 96 97 ...... to 104

we need to add first 11 digits that will be 9 + 3 +9 + 4 + 9 + 5 + 9 + 6 + 9 = 63 ,

This is the only series that will work

So sufficient,

II) statement

IF the average to digits are 9 then all digits are 9, Its not possible any other way,

For Nine 9 in at the last place. number must be 999999999.

We don't have any other information about the length of this integer, it can be 9 ( 20 times ) or 9 ( 9 times )
So i thought its insufficient.

Answer must be A,

Please tell me where i am wrong.

gdk800 wrote: If 11 consecutive integers are listed from least to most, which is the mean of the 11 digits?

fskilnik wrote:

gdk800 wrote: If 11 consecutive integers are listed from least to most, which is the mean of the 11 digits?

The first sentence of the question stem seems (at least) odd, because we do not know which 11 digits the question stem is refering too... "the 11 digits" is not properly defined, unless the 11 given integers are in fact 11 digits, what would be a particular case without any special "merit".

That´s why (I guess) beat_gmat_09 and myself considered the words "digits" in the question stem typos and that´s why I rephrased the question stem (substituting digits by integers... have a look at my post). IMHO the question makes more sense like that (because I do not believe the examiner/creator of the problem had in mind something like goyalsau imagined).

As far as the difference between digits and integers are concerned, (non-negative) digits are the integers 0,1,2, ...,9 only, as goyalsau mentioned. (I´ve never seen GMAT using "negative digits", by the way.)

Regards,
Fabio.

fskilnik wrote: P.S.: I know goyalsau question was addressed to Shovan, but I guess (and hope) neither him nor Shovan will be offended with my reply (both are some of my BTG friends, by the way). Anyway, goyalsau´s and Shovan´s feedback (not to mention beat_gmat_09´s) are more than welcomed, as usual, and I apologyse for any inconvenience my answer may have brought. (I am also a big fan of Mahatma, goyalsau.)

shovan85 wrote: Hi Fabio, Nice explanation. I (nor any of BTG members) will never mind if someone tries to help other. Thanks for taking charge and explaining the same.

fskilnik wrote:

gdk800 wrote:A sincere Thanks to all members for such detailed explanations.

Beautiful (and unfortunately very rare) attitude, gdk800. I thank YOU for your kind gesture and I hope to be able to "find" you in other BTG posts.

Cheers,
Fabio.