If R, S, and T are points on a line

AbeNeedsAnswers wrote:If R, S, and T are points on a line, and if R is 5 meters from T and 2 meters from S, how far is S from T ?

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

D

Source: Official Guide 2020

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

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: D

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Rich