Hi Rajorshi100,

This DS question involves a specific sequence called a "Fibonacci" sequence. A Fibonacci sequence adds 2 consecutive terms to figure out the "next" term.

As an example, here's a traditional Fibonacci sequence: 1, 1, 2, 3, 5, 8, 13, 21, etc.

1+1=2
1+2+3
2+3=5
3+5=8
etc.

The language in this sequence ("each term after S2 is equal to the stun of Sn-1 + Sn-2") describes a Fibonacci sequence. It's worth noting that this type of sequence can start with ANY 2 numbers.

We're told that the 1st term = 4. We're asked for the value of the 2nd term.

Fact 1: The 3rd term = 7

With this info, we know....

1st term + 2nd term = 3rd term
4 + 2nd term = 7

We can calculate that the 2nd term = 3
Fact 1 is SUFFICIENT

Fact 2: The 4th term = 10

From the prompt, we know that...

1st term + 2nd term = 3rd term

4 + 2nd term = 3rd term

With the info from this Fact, we know...

2nd term + 3rd term = 4th term

2nd term + 3rd term = 10

We end up with 2 variables and 2 unique equations:
4 + 2nd term = 3rd term
2nd term + 3rd term = 10

This is a "system" of equations and we CAN solve it with algebra (since it's a DS question, we don't have to though).
Fact 2 is SUFFICIENT

Final Answer: D

GMAT assassins aren't born, they're made,
Rich

Hi Rajorshi100,

This type of sequence notation is relatively rare on the GMAT (you might see it once, you might not see it at all), so don't worry too much about this prompt. The overall concept of sequences will show up on your Test a number of times though, so you have to get in the habit of pattern-matching. Sometimes you're told what the pattern is, sometimes you have to discover it.

GMAT assassins aren't born, they're made,
Rich