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Isn't it D?

Let n be no. of people.

(1) The number of people in the group is equal to the size of each person's contribution, in dollars
n = 36/n
n^2 = 36
Sufficient.

(2) If three more people joined the group, each person's individual contribution would fall by $2.
n+3 = (36/n)-2
n^2+5n-36=0
Sufficient.

Think your initial setup from the given question stem is incorrect, especially no (2). That is, I think it should be:

Let n be no. of people; Let m be the contribution per person. Therefore,
initial equation is:
m = 36/n

1) Given is n = m
so then the initial equation becomes n = 36/n => n= +-6 => 6
{sufficient}



2) Given is if n is increased by 3 (n+3), then m is decreased by 2 (m = m-2)
so then the initial equation becomes (36/(n+3)) = m-2

Therefore we have two equations:
36 = (n+3)(m-2) and
36/n = m

substituting the value of m in the equation 36 = (n+3)(m-2) will yield 6 and -9 and 6 would be the answer.

{sufficient}

Therefore it would be D.

D it is... same approach me too

Using information from statement 2 alone, how can you derive the equation 36/n = n?

Sorry. I think i solved this prob in a hurry.

Ok. Let's assume that m is the contribution of a member in group.

We know that m = 36/n from the question.

(2) m - 2 = 36/n+3

Sub. m=36/n,

36/n - 2 = 36/n+3

Now, you can solve to find out n (no. of people). Its sufficient.

Yeah think now you have it correct. However, duly note that in statement 2, the "n" on both side of the equation will like yield an "n^2" quad equation, which will require you to factor and hence will lead to two answers. If the two solutions for the n^2 yields two different positive values, then statement 2 will be "insufficient" and answer to the problem would have been A.

How do you get n^2 in statement II? Can you pls explain?

Sure, see my second post above under statement 2:

2) Given is if n is increased by 3 (n+3), then m is decreased by 2 (m = m-2)
so then the initial equation becomes (36/(n+3)) = m-2

Therefore we have two equations:
36 = (n+3)(m-2) and
36/n = m

substituting the value of m in the equation 36 = (n+3)(m-2) will yield 6 and -9 and 6 would be the answer.

{sufficient}

In your post you listed statement 2 as:
(2) m - 2 = 36/n+3

Sub. m=36/n,

36/n - 2 = 36/n+3 --> This means, (36/2) - (2/1) = (36/(n+3)). Hope this helps.