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Register now and save up to $200 Available with Beat the GMAT members only code • Get 300+ Practice Questions 25 Video lessons and 6 Webinars for FREE Available with Beat the GMAT members only code • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • 1 Hour Free BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Free Practice Test & Review How would you score if you took the GMAT Available with Beat the GMAT members only code ## OG12 #70 - value of n? Why isnt n =0 ?? This topic has 1 expert reply and 3 member replies rohit_gmat Master | Next Rank: 500 Posts Joined 16 Jun 2010 Posted: 158 messages Followed by: 1 members Thanked: 13 times #### OG12 #70 - value of n? Why isnt n =0 ?? Sun Oct 10, 2010 7:32 am Elapsed Time: 00:00 • Lap #[LAPCOUNT] ([LAPTIME]) Mary persuaded n friends to donate$500 each to her election campaign, and each of those n friends persuaded n more friends to donate $500 each to Mary's campaign. If no one donated more than once and if there were no other donations, what was the value of n? (1) The first n people donated 1/16 of the total amount donated (2) The total amount donated was$120,000.

The OA is D

But I thought B was the correct answer.
With both statments we get quadratic equations :
Statement 1 gives us : n =0 or 15
Statement 2 gives us : n = -16 or 15 (this is clear since -16 people is not possible, so 15 must be the value)
But GMAC says - "Assuming n>0" statement 1 gives us n = 15....... WHY CAN'T n = 0 ??
When can we assume in the GMAT that n>0?? And when can we not?? i.e. when the question doesn't clearly specify...

[/b]

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selango Legendary Member
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Sun Oct 10, 2010 8:02 am
rohit bro,

You mentioned that in stmt2 that n=-16 is not possible..then how come n=0 also possible?It means there are 0 number of friends (or) no friends at all(or) in this case no question at all unless the total amount is zero.
Here n represents number of friends.So we need to assume that n>0.

PS:By the way u think the question ll be stated in this way huh?

Mary persuaded n friends to donate $500 each to her election campaign, and each of those n friends persuaded n more friends to donate$500 each to Mary's campaign. If no one donated more than once and if there were no other donations, what was the value of n?
Note that n is an positive integer since it represent the number of friends.

Just Kidding yaar

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rohit_gmat Master | Next Rank: 500 Posts
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Sun Oct 10, 2010 7:39 pm
Hi Selango,

Im genuinely in doubt man!... I assumed n not equal to -16 since negative 16 is not a possible number of friends (or people)... but zero is... isnt it? ... Mary was probably a loser and had no friends who gave no money...??

Actually, after posting this I saw a post from another guy with a similar issue... and a GMAT guru advised that in the GMAT for real life problems, the trick is never "assuming 0".... theres another question in the OG abt 2 cities' populations and their leaders or smth like tht... and if one assumes that population is zero then the question goes crazy...

thanks for ur support anyway

Viktri Junior | Next Rank: 30 Posts
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Wed Oct 13, 2010 9:26 pm
Data given:

n x 500 + n x n x 500
total = 1500n

i) (n+500) x 16 = 1500n
solvable

ii) 1500n = 120,000
solvable

rohit_gmat wrote:
Mary persuaded n friends to donate $500 each to her election campaign, and each of those n friends persuaded n more friends to donate$500 each to Mary's campaign. If no one donated more than once and if there were no other donations, what was the value of n?
(1) The first n people donated 1/16 of the total amount donated
(2) The total amount donated was $120,000. The OA is D But I thought B was the correct answer. With both statments we get quadratic equations : Statement 1 gives us : n =0 or 15 Statement 2 gives us : n = -16 or 15 (this is clear since -16 people is not possible, so 15 must be the value) But GMAC says - "Assuming n>0" statement 1 gives us n = 15....... WHY CAN'T n = 0 ?? When can we assume in the GMAT that n>0?? And when can we not?? i.e. when the question doesn't clearly specify... [/b] ### GMAT/MBA Expert Testluv GMAT Instructor Joined 19 Oct 2009 Posted: 1302 messages Followed by: 162 members Thanked: 538 times GMAT Score: 800 Wed Oct 13, 2010 9:48 pm selango wrote: rohit bro, PS:By the way u think the question ll be stated in this way huh? Mary persuaded n friends to donate$500 each to her election campaign, and each of those n friends persuaded n more friends to donate \$500 each to Mary's campaign. If no one donated more than once and if there were no other donations, what was the value of n?
Note that n is an positive integer since it represent the number of friends.

Just Kidding yaar
...hilarious.

In PS word problems that describe a situation, you can always assume that the number of entities is such that the situation exists (this usually means that they are all positive integers.) Or as selango points out, if we let n = 0, then Mary has no friends, and there is no question at all (because the situation wouldn't exist).

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