BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

P is a polygon

Expert replies
by amsm25 » Fri Apr 27, 2012 3:06 am
P is a polygon. Is it possible to construct a circle such that each vertex of the polygon is a point on the circle?
1)All sides of the polygon are of equal length.
2)All Angles of the polygon have equal measures.



AO - B. Why can't it be D????
Join the discussion
Source: — Data Sufficiency |

by Shalabh's Quants » Fri Apr 27, 2012 4:22 am
amsm25 wrote:P is a polygon. Is it possible to construct a circle such that each vertex of the polygon is a point on the circle?
1)All sides of the polygon are of equal length.
2)All Angles of the polygon have equal measures.



AO - B. Why can't it be D????
Statement 1...

Imagine Rhombus. All sides are equal but one cannot have all 4 vertexes on a circle. Insuff.

Statement 2...

Imagine Rectangle. All angels are equal but one cannot have all 4 vertexes on a circle. Insuff.

So it should be C.
Shalabh Jain,
e-GMAT Instructor
Join the discussion

by 4GMAT_Mumbai » Fri Apr 27, 2012 6:52 am
Shalabh's Quants wrote:
Statement 2...

Imagine Rectangle. All angels are equal but one cannot have all 4 vertexes on a circle. Insuff.

C.
Agreed that statement 2 is insufficient.

However, a rectangle may not be the right example. Even a rectangle is a cyclic quadrilateral - i.e., a circle can always be drawn touching the 4 vertices of a rectangle.

Any quadrilateral whose opposite angles are supplementary is a cyclic quadrilateral (works vice versa also).

Statement 2 could be proved to be insufficient with a hexagon which looks like this ...
Image

If a circle is drawn which passes through the 3 vertices on the left portion of the hexagon, then, the other 3 vertices will not lie on the circle. This is, in spite of, all the angles being equal.

I hope this helps. Thanks.
Naveenan Ramachandran
4GMAT, Dadar(W) & Ghatkopar(W), Mumbai
Join the discussion

by ronnie1985 » Fri Apr 27, 2012 7:46 am
Equal chords subtend equal angle at the centre of the circle in question.

If all the angles of a polygon are equal it implies it is a cyclic polygon as it is the corollary of the theorem stated in the first sentence.
Follow your passion, Success as perceived by others shall follow you
Join the discussion

by Stuart@KaplanGMAT » Fri Apr 27, 2012 7:48 am
4GMAT_Mumbai wrote:
Shalabh's Quants wrote:
Statement 2...

Imagine Rectangle. All angels are equal but one cannot have all 4 vertexes on a circle. Insuff.

C.
Agreed that statement 2 is insufficient.

However, a rectangle may not be the right example. Even a rectangle is a cyclic quadrilateral - i.e., a circle can always be drawn touching the 4 vertices of a rectangle.

Any quadrilateral whose opposite angles are supplementary is a cyclic quadrilateral (works vice versa also).

Statement 2 could be proved to be insufficient with a hexagon which looks like this ...
Image

If a circle is drawn which passes through the 3 vertices on the left portion of the hexagon, then, the other 3 vertices will not lie on the circle. This is, in spite of, all the angles being equal.

I hope this helps. Thanks.
Umm.. not to be too picky, but the angles in your hexagon are NOT all equal (the 2 angles of the "pointy bits" are different from the other 4 angles).

Any polygon with equal angles is, in fact, cyclical.
Image

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
Join the discussion