Hi all!
This is a perfect question to slip and be "trapped", if you are not careful.
Before I move to the operation, lets deep think a bit.
r, s, and t are the absolute values of points R,S,T.
For example if S= 1, s=|1|=1
What exactly is Absolute value or the Mod function? The algebraic definition defines |x| = x if x>0 and -x if x<0. So |-1| = -(-1)=+1.
Okay!
With that thought at place, observe the point R. This is the link to your getting the question right if the GMAT thinking and observation is at place or wrong if you ignore the difference between R, r and the mod function rules(if you chose D)
R is to the left of 0.
What kind of number is to the left of 0? -A negative number ! Right?
What is the absolute value of a negative number? We started off with this definition!
|x| =-x when x<0
We are asked => the average (arithmetic mean) of the coordinates of the points R, S, and T ?This is R+S+T/3
There is no problem to see that S=s and T=t as both of these coordinates are to the right of 0 and positive. |x|=x when x>0
For R, the value of r = -R (Since r= |R| and R<0)
So value of the coordinate R= -r
Hence the average of the coordinates is R+S+T/3= -r+s+t/3 or option E.
Guard yourself against D(observation and gap of analysis) and B(Trapped due to low focus and loss of grip on the question).
If you have marked A or C, please go back to the fundamentals of absolute values. You need to enhance conceptual clarity.
If you got this question right, great
If NOT, what's there to lose? You only gain multiple perspectives from the Official Questions.
Let me know if you have any questions or concerns in the comments by tagging us.
Devmitra Sen
GMAT Mentor