Source: Official Guide Revised GRE 1st Ed. Part 8; Section 6; #3

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# AB is a diameter of the circle above

AB is a diameter of the circle above. Quantity A : The length of AB Quantity B : The average (arithmetic mean) of the lengths of AC and AD Quantity A is greater., Quantity B is greater., The two quantities are equal., The relationship cannot be determined from the information given.

### 3 Explanations

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Jorge Isaac Cordero Enriquez

Hi!

I had the same logic as Vishnu (as AC and AD can be freely moved, they can in fact become as long as the diameter).

So it is safe to assume that when dealing with diagrams, where we can move the geometry (lines, angles, etc), two elements cannot superpose?

Thanks!

Oct 5, 2017 • Comment

Jonathan , Magoosh Tutor

Hi Jorge! That's correct -- did you see my comment to Vishnu below?
You may find the following helpful as well:
GRE Geometry Diagram Assumptions - Magoosh GRE Blog
https://magoosh.com/gre/2013/gre-geometry-diagram-assumptions/

3

Here chord AC and AD can also be equal to diameter. Hence their average will equal to diameter AB. In this case, the answer will be D. Why arent we considering the AC and AD equal to diameter. The Largest chord is the diameter right?

May 21, 2015 • Comment

Jonathan , Magoosh Tutor

Vishnu, you're right that the diameter is the largest chord. However, although GRE diagrams are not drawn to scale, we CAN assume that segments that appear separate ARE separate. Therefore, AB, AC, and AD are different segments sharing the same vertex. There can only be one diameter from A. So if AB is the diameter, AC and AD cannot be diameters. I hope that helps.

2 Chris Lele, Magoosh Tutor

Oct 11, 2012 • Comment