Source: Official Guide for the GMAT 13th Ed. Data Sufficiency; #6 Official Guide for the GMAT 2015 14th Ed. Data Sufficiency; #6

3

A certain expressway has Exits J, K,

A certain expressway has Exits J, K, L, and M, in that order. What is the road distance from Exit K to Exit L?

3 Explanations

1

Gravatar Cydney Seigerman, Magoosh Tutor

Hi Vivian :)

As Sam mentions in his explanation, the difference between the two distances LM-KJ is not the same as the distance between KL. In this question, we originally have 3 unknowns: JK, KL, and LM. Let's look at the distances again:

JL=21 --> JK+KL=21
KM=26 --> KL+LM=26

If we subtract the distances, we have

26 - 21 = KL + LM - JK - KL = LM - JK = 5

Here, we're left with 2 unknowns but only 1 equation. And without knowing one of these two unknowns, we're unable to use this information in the equations above to solve for KL. This is another way to see why the statements are insufficient.

I hope this helps!

Feb 6, 2016 • Comment

1

Gravatar Sam Kinsman, Magoosh Tutor

Hi Vidyasagar, when we consider both statements together, we still don't have enough information to find the distance between any of the exits. The two distances we're given (26 and 21) could have any kind of overlap: it could by only 1 mile, or it could be 20 miles! The difference between 26 and 21 doesn't represent the distance between any of the exits.

Oct 18, 2015 • Comment

1

Gravatar Mike McGarry, Magoosh Tutor

Dec 28, 2013 • Comment

Vidyasagar Mohan Ram

Thanks Mike for the detailed explanation, just out of curiosity, can we relate the difference of 26 and 21 to be the distance between any of the exits ?

Sep 11, 2015 • Reply

Vivian M Graves

How come we can't subtract the two distances? wouldn't the difference give you the amount of KL?

Jan 26, 2016 • Reply

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Section 6.3 Data Sufficiency

Section 6.3 Data Sufficiency

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