Question 1963: in an attempt to discreadit the persident, a member of the opposite political party wishes to start a scandakous rumor about him. he plans to tell people this rumor one week before the election day and wants the entire population of the united staes (that's 250,000,000 people!) to know the rumor. he needs to figure out how many people he should tell (and they each will tell the same number of people) so that everyone will have heard the rumor by the seventh day.
Answer by longjonsilver(2297)   (Show Source):
You can put this solution on YOUR website! this is a geometric progression (GP), where you start with a value and then multiply a fixed amount to each subsequent value, so for example...
1 + 2 + 4 + 8 + 16 + 32 + 64 = whatever... this is starting with 1 and multiplying 2 to each value.
the issue with your question, which is always debateable...do we start with 1 person (ie the man in question) or do we start with the number of people he just told...call it x? Also, where do we start from and where do we end? Beginning of DAY1 with himself?
Beginning of DAY1 with x people?
End at START of DAY7 with people telling their next lot?
basically it will either be
 =250,000,000
or
 =250,000,000
This is nothing to do with you, just the question being ambiguous.
As to how to solve this, well that is another question :-).
For a GP, starting at a with constant ratio r over n terms, the sum of these is given by the formula 
here, a will be 1 or x
r will be x
n will be 7
and the sum itself will be 250,000,000. You will need to find x.
Jon
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