Data Sufficiency

Hi,

How would you explain the answer to this question?

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

Cheers,

OA is D.

From 1st , 500n = (1/16)(500n + 500 n^2) Can be solved for n

From 2nd, 500n + 500 n^2 = 120000 , can be solved for n.

Hence D

Edit: Oh yeah, statement 1 is sufficient :p

IMO [spoiler](D)[/spoiler]

My Math formula for this:

Draw 2 sticks, for each stick draw 2 more
This equal a total of 2 + 4 sticks

Draw 3 sticks, for each stick draw 3 more
This equal a total of 3 + 9 sticks

So the formula here is n + n^2 to get the number of people
Now to get the amount of money we must multiply by 500:
500n + 500n^2 = Total Money

1) tell us that 500n = 1/6 * (Total Money)
500n = 1/6 (500n + 500n^2) can be solved for n

2) give us the "Total Money" so if we apply the formula we get:
500n + 500n^2 = 120,000 -> which is a Quadratic equation that can be solved for n.

ccassel wrote:Hi,

How would you explain the answer to this question?

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

Cheers,

That is great. Thanks.

I was trying to plug in and work backwards but with quadratic equations it proves very difficult.

Cheers,