Since this DS is in English we read it straight --> Mary persuaded/they donated - count n*500, next EACH of n persuaded n more people (n MORE means
+n, BUT here it means n, which is incorrect, and I guess OUT of GMAT scope, this problem could never be from OG 11 or 12, my personal opinion) - count final expression as n*
(n)*500. We are asked to find the value of n with the given conditions - let's call total donation X, and we know that n*500 +n*(n)*500=X finalizing 500n(1+n)=X
st(1) ponder before writing, each donated $500 and first donations came from n people --> 16(n*500)=X, enough? Yes, 16(n*500)=500n(1+n), Cancel n and 500 on both sides (we cancel n as n CANNOT be 0) --> 16=(1+n), n=15
st(2) X=120,000 OR 500n(1+n)=120,000 here from the both side we MAY cancel zeros and numbers --> n(1+n)=240. Now to solve for n we can find approximate square of 240 and +-1 number next to it. Let's try 15^2 should work, as we get 15*16 which is 15*(15+1)=230 Sufficient
answer D.
anirudhbhalotia wrote: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 1/16 of the total amount donated.
2. The total amount donated was $120,000
OA- D
My knowledge frontiers came to evolve the GMATPill's methods - the credited study means to boost the Verbal competence. I really like their videos, especially for RC, CR and SC. You do check their study methods at
https://www.gmatpill.com
