Second to last term

[beat_gmat_09]

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

[Rahul@gurome]

Let the sequence is r, 3r, 9r, 27r....

(1) It's given that r = 3. So 4th term = 27 * 3 = 81
So, (1) is SUFFICIENT.

(2) The second-to-last term does not give is the information about the first term and hence the 4th term.
So, (2) is NOT SUFFICIENT.

The correct answer is [spoiler](A)[/spoiler].

[beat_gmat_09]

Let the sequence is r, 3r, 9r, 27r....

(1) It's given that r = 3. So 4th term = 27 * 3 = 81
So, (1) is SUFFICIENT.

(2) The second-to-last term does not give is the information about the first term and hence the 4th term.
So, (2) is NOT SUFFICIENT.

The correct answer is [spoiler](A)[/spoiler].

Cant we know the first term by knowing the ques stmt and (2) -> 3^10, as 3.
the sequence becomes 3, 3^2, 3^3 .... 3^10
in what other cases could second-to last term come out as 3^10 knowing tht each term is 3 times the previous ?

[Rahul@gurome]

Cant we know the first term by knowing the ques stmt and (2) -> 3^10, as 3.
the sequence becomes 3, 3^2, 3^3 .... 3^10
in what other cases could second-to last term come out as 3^10 knowing tht each term is 3 times the previous ?

The main question says that "each term is three times the previous term", and (2) says that second-to last term is 3^10, but combining this information we cannot say that the sequence is definitely starting from "3", it can also start from 3^2 or 3^3, and so it's 4th term will keep on changing.
Does that answer your query?

[beat_gmat_09]

Cant we know the first term by knowing the ques stmt and (2) -> 3^10, as 3.
the sequence becomes 3, 3^2, 3^3 .... 3^10
in what other cases could second-to last term come out as 3^10 knowing tht each term is 3 times the previous ?

The main question says that "each term is three times the previous term", and (2) says that second-to last term is 3^10, but combining this information we cannot say that the sequence is definitely starting from "3", it can also start from 3^2 or 3^3, and so it's 4th term will keep on changing.
Does that answer your query?

Got it.