Lesson: Circles

Comment on Circles

Thank you for your prompt response elsewhere.

I could not even understand what is being asked

https://gmatclub.com/forum/the-center-of-a-circle-is-5-2-5-7-is-outside-the-circle-189027.html
Possible values of r? One radius for a circle right?
gmat-admin's picture

https://gmatclub.com/forum/a-circle-with-center-1-0-and-radius-2-lies-in-the-coordinate-plane-275642.html

I didn't draw out a figure like you did in the approach. The way I approached this was to determine if both x and y were points that were in Q2.

So statement 1 and 2 by itself were clearly insufficient. Combined, they still gave the information that both x and y could lie on the negative and positive sides on the plane.

Is this approach ok? Also, if the statements showed that x and y could be 0 (point of origin) and nothing more, then I'm guessing this doesn't count as it doesn't tell us if the line passes through Q2
gmat-admin's picture

Question link: https://gmatclub.com/forum/a-circle-with-center-1-0-and-radius-2-lies-in...

That approach works.
Since the circle does not pass through the origin, x and y cannot both equal zero.

Cheers,
Brent

But if the circle did pass through the origin with x and y both being equal to zero in the two statements, would that be sufficient to prove that the circle passes through Q2? Or could we still prove that it doesn't as the part of the circle that passes through the origin is at the outermost edge (i.e. it touches the origin and sits on Q1 and Q4).
gmat-admin's picture

The point (0,0) is not in any of the quadrants. That is, we cannot say that (0,0) is in Quadrant 2.

That said, I'm pretty sure the test-makers won't create a question that relies solely on that fact.

Cheers,
Brent

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