一道GWD数学题求教

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.

答案是D 没有问题 但是根据(2)似乎求出来的人数不是整数?期待NN解答!!!

LZ(1)是没有写全吧？

(2): 500*(n^2+n)=120,000   n=15

2算出来是整数啊

500n + 500 n^2 =120000

n+n^2=240

n(n+1)=240

n=15