another gem

by **barlie** Tue Aug 28, 2007 1:42 pm

In a sequence of terms in which each term is three times the previous term, what is the fourth term?

(1) The first term is 3.

(2) The second to last term is 3^10.

Assume first one is x. the sequence can be expressed as x, 3x, 9x, 27x
This is a geometric progression
1) is sufficent to determine fourth
2) is sufficent knowing that 9x = 3^10.

However the explaination is given as
(2) INSUFFICIENT: We can use this information to find the last term and previous terms, however, we don't know how many terms there are between the second to last term and the fourth term.

:?:

In english please ??

by **StaceyKoprince** Tue Aug 28, 2007 10:10 pm

Hi, again, please post the author / source of the question.

But just a language thing: just because someone asks you for the 4th term does not mean that the 4th term is also the last term. The last term could be the 10th term or the 12th term or the 84th term...

Assume nothing on data sufficiency!