Each statement is individually Sufficient.

Refer to the attached figure.

D is the answer.

We know that \(RT=5\) and \(RS=2\). The original question: \(ST=?\)

1) We know that \(R\) is between \(S\) and \(T\). It doesn't matter whether \(S\) is to the left of \(T\) or \(S\) is to the right of \(T\) since \(ST=RT+RS=5+2=7\) in both cases. Thus, the answer to the original question is a unique value. \(\implies\) Sufficient

2) We can infer that \(R\) is between \(S\) and \(T\), so \(ST=7\) again. Thus, the answer to the original question is a unique value. \(\implies\) Sufficient

Answer: D
_________________

Given: R, S, and T are points on a line, and if R is 5 meters from T and 2 meters from S
There are 4 possible scenarios that meet the above conditions:


Target question: How far is S from T?

Statement 1: R is between S and T.
When we check the 4 possible scenarios, we see that scenarios #2 and #3 meet the conditions of statement 1
For both scenarios, the answer to the target question is the distance from S to T is 7
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: S is to the left of R, and T is to the right of R.
When we check the 4 possible scenarios, we see that only scenario #2 meets the conditions of statement 2
For scenario #2, the answer to the target question is the distance from S to T is 7
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: D

Cheers,
Brent
_________________

We are given the distance from R to T and from R to S; and we need to determine the distance from S to T. To be able to determine the distance from S to T, we need to know in what order R, S and T are positioned on the line.

Statement One Alone:

R is between S and T.
Since R is between S and T, the distance between S and T is equal to the sum of the distances from R to T and from R to S. Since we are given both of those distances, we have enough information to calculate the distance from S to T. Statement one alone is sufficient.

Eliminate answer choices B, C and E.

Statement Two Alone:

S is to the left of R, and T is to the right of R.

Notice that this could only happen if R is between S and T. If R is not between S and T, either both S and T are to the left of R or both S and T are to the right of R. Since we know R is between S and T, we can proceed as in the previous statement to calculate the distance between S and T. Statement two alone is sufficient.

Eliminate answer choice A.

Answer: D
_________________

Hi All,

We're told that R, S, and T are points on a line, R is 5 meters from T and R is 2 meters from S. We're asked for the distance between S and T. This question can be solved with a bit of logic and Arithmetic (and you might find it helpful to draw some actual number lines).

(1) R is between S and T.

With the information in Fact1, we know that R is somewhere between S and T. Regardless of where you place those 3 values on a number line, since R is 5 meters from S and 2 meters from T, then the line ST will be exactly 5+2 = 7 meters in length.
Fact 1 is SUFFICIENT

(2) S is to the left of R, and T is to the right of R.

The information in Fact 2 takes the information that's in Fact1 and 'restricts' it a bit more (placing S to the 'left' and T to the 'right' - relative to R's position - on the number line. The deduction that we made in Fact1 also applies to Fact2. ST will be exactly 5+2 = 7 meters in length.
Fact 2 is SUFFICIENT

Final Answer:

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

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________