If the 3rd term of sequence A is 15 and all of the terms in

[BTGmoderatorDC]

If the 3rd term of sequence A is 15 and all of the terms in the sequence are positive, then what is the 2nd term?

1) The 1st term of A is 5.
2) Each term of A after the 1st term is y times the preceding term.

OA C

Source: EMPOWERgmat

[Jay@ManhattanReview]

If the 3rd term of sequence A is 15 and all of the terms in the sequence are positive, then what is the 2nd term?

1) The 1st term of A is 5.
2) Each term of A after the 1st term is y times the preceding term.

OA C

Source: EMPOWERgmat

Let's take each statement one by one.

1) The 1st term of A is 5.

Since the relationship between the 1st term and the 3rd term is not given, we can't get the 2nd term. Insufficient,

2) Each term of A after the 1st term is y times the preceding term.

Say the first term is a. Thus, the 2nd term = ay and the 3rd term = ay^2. Thus, ay^2 = 15. Since we have two variables a and y, we can't get their unique values, thereby can't get the value of the 2nd term ay. Insufficient.

(1) and (2) together

From (1), we have a = 5 and from (2), we have ay^2 = 15. Thus, ay^2 = 15 => 5*y^2 = 15 => y = √3

Thus, the 2nd term = ay = 5*√3. Sufficient.

The correct answer: C

Hope this helps!

-Jay
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