That's an interesting question and one that I asked in a previous post because the directions do not explicitly state that "if a point appears to be on a line it actually is on that line." But the general consensus was that that had to be assumed.StuartM wrote:Thanks for the reply, guys.
But my question is how can we assume line OP = radius? While it looks like that's the case from the diagram, it cannot be assumed from the question/statements, can it?
I recently created a video that outlines what can and cannot be assumed in GMAT Geometry questions.ldoolitt wrote:That's an interesting question and one that I asked in a previous post because the directions do not explicitly state that "if a point appears to be on a line it actually is on that line." But the general consensus was that that had to be assumed.StuartM wrote:Thanks for the reply, guys.
But my question is how can we assume line OP = radius? While it looks like that's the case from the diagram, it cannot be assumed from the question/statements, can it?
O is stated to be the center and also one vertex of the desired polygon. P is another vertex and appears to also lie on the circle with center O. Therefore, by definition, OP is a radius of circle O. But yes, you have to assume that the point is actually on the circle because it appears to be on the circle.
Well, even if the world does end tomorrow, you can be at peace with the fact that you know how to solve Data Sufficiency questionsStuartM wrote:Thanks, Brent. Really helpful.
Still seems a bit arbitrary - that if you assume two lines are parallel in a DS question, you can (will most likely) get the question wrong, yet if you don't assume two assume lines intersect at an exact point, you also get the question wrong!
C'est la vie. I assume that the world won't end tomorrow and all my GMAT study won't have been in vain!
The instructions actually don't say that they are not accurate to scale. It just says "figures are drawn as accurately as possible." So, for example, we know it's not safe to assume two lines that appear parallel are actually parallel but it is safe to assume that if a point appears to be on a line that is actually on that line.isanju wrote:One little question: When the instructions say that the figures are not accurate to the scale, does it mean that they are illusive (meaning the point on the line is not actually on the line)?
The point is, even if the figure is not drawn to the scale, the point that has been shown on a particular line, should be on that line irrespective of the scale. So, why do we need to assume anything when it is given in the question?
For DS, the instructions Do say that diagrams are not drawn to scale. From the Official Guide (p24 of 12th ed.):ldoolitt wrote:
The instructions actually don't say that they are not accurate to scale. It just says "figures are drawn as accurately as possible." So, for example, we know it's not safe to assume two lines that appear parallel are actually parallel but it is safe to assume that if a point appears to be on a line that is actually on that line.
Its just weird GMAT quirkiness that you need to know for the test.
Based on the first point, we know that DS diagrams are not necessarily drawn to scale and we can't rely on the way that they appear.Figures:
Figures conform to the information given in the question, but will not necessarily conform to the additional information given in statements (1) and (2).
Lines shown as straight are straight, and lines that appear jagged are also straight.
The position of points, angles, regions, etc., exist in the order shown, and angle measures are greater than zero.
All figures lie in a plane unless otherwise indicated.
[/list]All figures accompanying problem solving questions are intended to provide information useful in solving the problems. Figures are drawn as accurately as possible.
Oh yeah, that is true for the statements in DS questions. I was more thinking of PS questions and the question stem in DS questions which that statement says "conforms to the information given in the question." That was my fault for making that unclear statement but I agree with that.Stuart Kovinsky wrote:
Based on the first point, we know that DS diagrams are not necessarily drawn to scale and we can't rely on the way that they appear.
I dunno, maybe it means x coordinate in order or y coordinate in order. At best its a weak inference. Obviously inductively we know that all points that appear to be on a line are on a line, since I've never encountered a problem for which that isn't true (which I guess makes this discussion moot). But deductively from the instructions I don't see how that can be inferred.Stuart Kovinsky wrote: Based on the third point, we know that points exist in the order shown; so, if a point appears on a line, it must be on that line (otherwise how could it be in order?).
