Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

For a circle with center point P, cord XY is the [#permalink]

Show Tags

08 Feb 2012, 18:44

3

This post received KUDOS

11

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

95% (hard)

Question Stats:

45% (02:34) correct
55% (02:10) wrong based on 378 sessions

HideShow timer Statistics

Attachment:

Untitled.png [ 4.33 KiB | Viewed 7533 times ]

For a circle with center point P, cord XY is the perpendicular bisector of radius AP (A is a point on the edge of the circle). What is the length of cord XY?

(1) The circumference of circle P is twice the area of circle P. (2) The length of Arc XAY = \(\frac{2\pi}{3}\).

How come the answer is D? I have drawn these pictures as they were not provided with the questions. Even though with my guess work I have selected A which is incorrect. Can someone please let me know how to solve this? Also, I understand this will include a concept of 30-60-90 degree triangle - any idea which angles to assign 30 and 60 degrees?

For a circle with center point P, cord XY is the perpendicular bisector of radius AP (A is a point on the edge of the circle). What is the length of cord XY?

From the diagram and the stem: AZ=ZP=r/2. In a right triangle ZPX ratio of ZP to XP is 1:2, hence ZPX is a 30-60-90 right triangle where the sides are in ratio: \(1:\sqrt{3}:2\). The longest leg is ZX which corresponds with \(\sqrt{3}\) and is opposite to 60 degrees angle. Thus <XPY=60+60=120

(1) The circumference of circle P is twice the area of circle P --> \(2\pi{r}=2*\pi{r^2}\) --> \(r=1\) --> \(XZ=\frac{\sqrt{3}}{2}\) --> \(XY=2*XZ=\sqrt{3}\). Sufficient.

(2) The length of Arc XAY = 2pi/3 --> \(\frac{2\pi}{3}=\frac{120}{360}*2\pi{r}\) --> \(r=1\), the same as above. Sufficient.

Re: For a circle with center point P, cord XY is the [#permalink]

Show Tags

11 Feb 2012, 12:29

Sorry Bunuel - in your explanation, how come longest leg be ZX? I think it should be XP because that's opposite to 90 degree angle. Also, do you mind telling me how did you find out which side will correspond to 60 degree and 30 degree angle?
_________________

Sorry Bunuel - in your explanation, how come longest leg be ZX? I think it should be XP because that's opposite to 90 degree angle. Also, do you mind telling me how did you find out which side will correspond to 60 degree and 30 degree angle?

XP is hypotenuse, which obviously is the longest side but the longest leg is ZX (so the second longest side).

In a right triangle where the angles are 30°, 60°, and 90° the sides are always in the ratio \(1 : \sqrt{3}: 2\). Notice that the smallest side (1) is opposite the smallest angle (30°), and the longest side (2) is opposite the largest angle (90°). Since the ratio of the leg ZP to the hypotenuse XP is 1:2, then ZP (the shortest side) corresponds to 1 and thus is the opposite of the smallest angle 30°, which means that another leg ZX corresponds to \(\sqrt{3}\).

Sorry Bunuel - still struggling. How did you get XZ = sqrt3/2? Apologies for been a pain.

It's not a problem at all.

Since \(\frac{XZ}{XP}=\frac{\sqrt{3}}{2}\) (from 30°, 60°, and 90° right triangle ratio) and \(XP=r=1\) then \(\frac{XZ}{1}=\frac{\sqrt{3}}{2}\) -->\(XZ=\frac{\sqrt{3}}{2}\).

Re: For a circle with center point P, cord XY is the [#permalink]

Show Tags

10 Mar 2012, 00:20

1

This post received KUDOS

enigma123 wrote:

(2) The length of Arc XAY = 2p/3.

Why does it read 2p/3. Shouldn't it be 2pi/ 3 atleast, if you aren't putting the symbol for pi? That completely threw me off and I was left wondering, "does he mean 2(perimeter)/3? What does p stand for?"
_________________

If you like it, Kudo it!

"There is no alternative to hard work. If you don't do it now, you'll probably have to do it later. If you didn't need it now, you probably did it earlier. But there is no escaping it."

Why does it read 2p/3. Shouldn't it be 2pi/ 3 atleast, if you aren't putting the symbol for pi? That completely threw me off and I was left wondering, "does he mean 2(perimeter)/3? What does p stand for?"

You could check the correct reading (\(\frac{2\pi}{3}\)) of the statement in my post above, though I edited the initial post to avoid confusion in others. Thanks for suggestion. +1.
_________________

For a circle with center point P, cord XY is the perpendicular bisector of radius AP (A is a point on the edge of the circle). What is the length of cord XY?

From the diagram and the stem: AZ=ZP=r/2. In a right triangle ZPX ratio of ZP to XP is 1:2, hence ZPX is a 30-60-90 right triangle where the sides are in ratio: \(1:\sqrt{3}:2\). The longest leg is ZX which corresponds with \(\sqrt{3}\) and is opposite to 60 degrees angle. Thus <XPY=60+60=120

(1) The circumference of circle P is twice the area of circle P --> \(2\pi{r}=2*\pi{r^2}\) --> \(r=1\) --> \(XZ=\frac{\sqrt{3}}{2}\) --> \(XY=2*XZ=\sqrt{3}\). Sufficient.

(2) The length of Arc XAY = 2pi/3 --> \(\frac{2\pi}{3}=\frac{120}{360}*2\pi{r}\) --> \(r=1\), the same as above. Sufficient.

Answer: D.

Hi Bunuel,

How did you assume ZPX is a 30-60-90 right triangle just from the ratio of ZP to XP (1:2). How can we assume in any triangle if the two sides are in the ratio 1:2, it will be a 30-60-90 triangle?

I thought we have to know we have to know that the triangle is 30-60-90 triangle beforehand to calculated the third side based on the ratio of two given sides.

For a circle with center point P, cord XY is the perpendicular bisector of radius AP (A is a point on the edge of the circle). What is the length of cord XY?

From the diagram and the stem: AZ=ZP=r/2. In a right triangle ZPX ratio of ZP to XP is 1:2, hence ZPX is a 30-60-90 right triangle where the sides are in ratio: \(1:\sqrt{3}:2\). The longest leg is ZX which corresponds with \(\sqrt{3}\) and is opposite to 60 degrees angle. Thus <XPY=60+60=120

(1) The circumference of circle P is twice the area of circle P --> \(2\pi{r}=2*\pi{r^2}\) --> \(r=1\) --> \(XZ=\frac{\sqrt{3}}{2}\) --> \(XY=2*XZ=\sqrt{3}\). Sufficient.

(2) The length of Arc XAY = 2pi/3 --> \(\frac{2\pi}{3}=\frac{120}{360}*2\pi{r}\) --> \(r=1\), the same as above. Sufficient.

Answer: D.

Hi Bunuel,

How did you assume ZPX is a 30-60-90 right triangle just from the ratio of ZP to XP (1:2). How can we assume in any triangle if the two sides are in the ratio 1:2, it will be a 30-60-90 triangle?

I thought we have to know we have to know that the triangle is 30-60-90 triangle beforehand to calculated the third side based on the ratio of two given sides.

Notice that since XY is the perpendicular to AP, then ZPX is a right triangle with right angle at Z. So, we have that side:hypotenuse=1:2, which means that we have 30-60-90 triangle, where the ratio of the sides is \(1:\sqrt{3}:2\).
_________________

Re: For a circle with center point P, cord XY is the [#permalink]

Show Tags

17 Jul 2013, 10:50

Thanks for you reply Bunuel.

However, I still did not understand. Here we have angle XZP=90, XP=r and ZP=r/2.

We do not know that the other angles are 60 and 30 respectively. How can we use the ratio of two sides not three to conclude that it is a 30-60-90 triangle?

Should we know beforehand that it is a 30-60-90 triangle to use two sides to calculate the third one?

However, I still did not understand. Here we have angle XZP=90, XP=r and ZP=r/2.

We do not know that the other angles are 60 and 30 respectively. How can we use the ratio of two sides not three to conclude that it is a 30-60-90 triangle?

Should we know beforehand that it is a 30-60-90 triangle to use two sides to calculate the third one?

When we know two sides in a right triangle the third one is fixed.

We have side:hypotenuse=1x:2x --> third side = \(\sqrt{(2x)^2-x^2}=\sqrt{3}*x\), so the sides are in the ratio: \(1:\sqrt{3}:2\) --> 30-60-90 triangle.

Re: For a circle with center point P, cord XY is the [#permalink]

Show Tags

17 Jul 2013, 10:57

Bunuel wrote:

keenys wrote:

Thanks for you reply Bunuel.

However, I still did not understand. Here we have angle XZP=90, XP=r and ZP=r/2.

We do not know that the other angles are 60 and 30 respectively. How can we use the ratio of two sides not three to conclude that it is a 30-60-90 triangle?

Should we know beforehand that it is a 30-60-90 triangle to use two sides to calculate the third one?

When we know two sides in a right triangle the third one is fixed.

We have side:hypotenuse=1x:2x --> third side = \(\sqrt{(2x)^2-x^2}=\sqrt{3}*x\), so the sides are in the ratio: \(1:\sqrt{3}:2\) --> 30-60-90 triangle.

Does this make sense?

Thanks Bunuel. Now it makes complete sense.

I missed the last part in calculating the third side using Pythagoras.

Re: For a circle with center point P, cord XY is the [#permalink]

Show Tags

03 Sep 2013, 00:27

Quote:

We have side:hypotenuse=1x:2x --> third side = \(\sqrt{(2x)^2-x^2}=\sqrt{3}*x\)

I wonder if this is just today...that I am looking at this perfectly clear explanation and still do not get it. I did a couple of minutes later. So first of - thanks for detailed explanations Bunuel and others. I just wanted to add that \((2x)^2-x^2 = 3x^2\) for those who look at the formula with a predetermined mind so focused on that formula and as a result forget to calculate this basic stuff, perhaps wondering where that \(\sqrt{3}*x\) came from. It is possible it is just me, but it often appears to me that it is not. This is one of those..."duuuhhh"s
_________________

There are times when I do not mind kudos...I do enjoy giving some for help

Re: For a circle with center point P, cord XY is the [#permalink]

Show Tags

03 Sep 2013, 05:19

Bunuel wrote:

keenys wrote:

Thanks for you reply Bunuel.

However, I still did not understand. Here we have angle XZP=90, XP=r and ZP=r/2.

We do not know that the other angles are 60 and 30 respectively. How can we use the ratio of two sides not three to conclude that it is a 30-60-90 triangle?

Should we know beforehand that it is a 30-60-90 triangle to use two sides to calculate the third one?

When we know two sides in a right triangle the third one is fixed.

We have side:hypotenuse=1x:2x --> third side = \(\sqrt{(2x)^2-x^2}=\sqrt{3}*x\), so the sides are in the ratio: \(1:\sqrt{3}:2\) --> 30-60-90 triangle.

Does this make sense?

Bunuel,

If 2 pi r = 2 pi r^2

then either r=0 or r=1

Since radius is always +ve, its safe to assume that r=1. Is that correct?
_________________

However, I still did not understand. Here we have angle XZP=90, XP=r and ZP=r/2.

We do not know that the other angles are 60 and 30 respectively. How can we use the ratio of two sides not three to conclude that it is a 30-60-90 triangle?

Should we know beforehand that it is a 30-60-90 triangle to use two sides to calculate the third one?

When we know two sides in a right triangle the third one is fixed.

We have side:hypotenuse=1x:2x --> third side = \(\sqrt{(2x)^2-x^2}=\sqrt{3}*x\), so the sides are in the ratio: \(1:\sqrt{3}:2\) --> 30-60-90 triangle.

Does this make sense?

Bunuel,

If 2 pi r = 2 pi r^2

then either r=0 or r=1

Since radius is always +ve, its safe to assume that r=1. Is that correct?

Yes, because we obviously have a circle.
_________________

Re: For a circle with center point P, cord XY is the [#permalink]

Show Tags

28 Feb 2014, 08:19

Hey!

Could someone please check my calculations? I keep getting a wrong answer (I tried to solve it in a slightly different way but nonetheless the solution should be the same) for statement 1:

so, according to statement 1 --> 2pir=2pir² <=> r=1 ; for the following calculations, please see the attached image below.

--> (1) in (2): 90°-m°+p°=90° --> m°=p°, similarly: n°=w° ----> AXZ and XZB are similar triangles, hence, their side ratios will be equal. --> (XZ/0.5)=(0.75/XZ) <=>2XZ=(3/4XZ) <=> XZ²=3/8 <=> XZ=0.5(3/2)^(1/2) --> XZ=2XZ=(3/2)^(1/2)

I tried the calculations again and again, but i keep getting the same wrong answer and not 3^(1/2). What did I do wrong? I know that the 30-60-90 approach is easier and probably quicker but I am still confused about what error I made in my calculations/ approach. If someone can help, please do so

Max

Attachments

chord-problem.jpg [ 34.19 KiB | Viewed 6688 times ]

Could someone please check my calculations? I keep getting a wrong answer (I tried to solve it in a slightly different way but nonetheless the solution should be the same) for statement 1:

so, according to statement 1 --> 2pir=2pir² <=> r=1 ; for the following calculations, please see the attached image below.

--> (1) in (2): 90°-m°+p°=90° --> m°=p°, similarly: n°=w° ----> AXZ and XZB are similar triangles, hence, their side ratios will be equal. --> (XZ/0.5)=(0.75/XZ) <=>2XZ=(3/4XZ) <=> XZ²=3/8 <=> XZ=0.5(3/2)^(1/2) --> XZ=2XZ=(3/2)^(1/2)

I tried the calculations again and again, but i keep getting the same wrong answer and not 3^(1/2). What did I do wrong? I know that the 30-60-90 approach is easier and probably quicker but I am still confused about what error I made in my calculations/ approach. If someone can help, please do so

Max

\(\frac{XZ}{AZ} = \frac{ZB}{XZ}\) --> \(AZ = 0.5\) and \(ZB = 1.5\), not 0.75.

Re: For a circle with center point P, cord XY is the [#permalink]

Show Tags

01 Mar 2014, 05:17

enigma123 wrote:

Attachment:

Untitled.png

For a circle with center point P, cord XY is the perpendicular bisector of radius AP (A is a point on the edge of the circle). What is the length of cord XY?

(1) The circumference of circle P is twice the area of circle P. (2) The length of Arc XAY = \(\frac{2\pi}{3}\).

How come the answer is D? I have drawn these pictures as they were not provided with the questions. Even though with my guess work I have selected A which is incorrect. Can someone please let me know how to solve this? Also, I understand this will include a concept of 30-60-90 degree triangle - any idea which angles to assign 30 and 60 degrees?

hi bunuel ! can u please explain the 2nd condition how did we get 120 degree ?

gmatclubot

Re: For a circle with center point P, cord XY is the
[#permalink]
01 Mar 2014, 05:17

After days of waiting, sharing the tension with other applicants in forums, coming up with different theories about invites patterns, and, overall, refreshing my inbox every five minutes to...

I was totally freaking out. Apparently, most of the HBS invites were already sent and I didn’t get one. However, there are still some to come out on...

In early 2012, when I was working as a biomedical researcher at the National Institutes of Health , I decided that I wanted to get an MBA and make the...