Q11:

Mary persuaded n friends to donate $500 each to her election campaign, and then each of these n friends persuaded n more people 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 of the total amount donated.

(2) The total amount donated was $120,000.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient

答案给的是D,可我怎么都觉得是C,望高人指教.

你的题目上打掉了1/16

（1）500n=1/16[n(n+1)500](2)500n(n+1)=120000

The right answer is A, because from 500n(n+!)=120000 we cannot get the integral n.