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Official Guide Sequence & Series Question

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Newbie | Next Rank: 10 Posts
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by mdurlak » Fri Oct 01, 2010 12:30 pm
Hey Guys,

I'm struggling with question #45 on page 276 in the most up-to-date version of the Official Guide.

Can anyone help me out?

Here's the question:
"If r is a constant and an = rn for all positive integers n, for how many values of 'n' is an<100

(i) a50 = 500
(ii) a100 + a105 = 2,050

Thanks in advance!!
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by clock60 » Fri Oct 01, 2010 1:20 pm
to me the ans is D
from the problem
a1=1r
a2=2r
a3=3r.....
(1) a50=50r, 50r=500, r=10, so i hope that 9 values of n (1*10, 2*10,.......9*10) are less than 100

(2) the same operation
a100=100r
a105=105r. 100r+105r=205r=2050, r=10

by the way, what is most up-to-date version of OG??? they published the next edition?(other that 12 and supplements)
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by mdurlak » Fri Oct 01, 2010 1:53 pm
Hey,

Thanks a bunch, that really helps. I guess I was confused as to what the question was.

The newest version is 12 .... sorry if I confused you!

Thanks a bunch — it sure does look like you're on your way towards beating the Gmat. :)
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