Answer is (D).
Solution:
According to question, we try to derive the number of people then we come to know that there are n * (n+1) people are there.
HOW? for example there are 3 friends of Mary, so now each of the friend would ask help to their respective 3 friends.
Mary's friends = 3
Friends's friends = 3 X 3
Therefore total friends = 12 i.e 3 X 4
So, I guess, now you know how I have derived the formula.
So now with statement 1: 1/16 of total money is donated by Mary's n friends.
On the first look, its really hard to formulate any formula by just looking at the statement 1. so lets better try with statement 2.
On looking at statement 2,
we comet to know that n * (n + 1) * 500 = 120,000. So n = 15
So, statement (B) is alone sufficient.
Now, again looks at statement 1 which states that 1/16 of total money is mary's friend. That is 15/16 of total money is deposited by mary's friends' friends. Now, it looks very clear that there are 15 friends of mary who has deposited 1/16 of money.
Still didn't get???
Okay let me try to explain it in more details (how ever it still very confusing).
1/16 of total money means 1/16 of totals person who donated the money. 1/16 persons means 1/16 of n * (n + 1). So, now as persons are divided into 16 groups (because value is 1/16) so n + 1 = 16. (Remember n can't be equal to 16, as there are only 16 groups).
So n = 15.
So both statements are alone able to satisfy the answer.
Let me know the real answer.
