It is currently 23 Jun 2017, 15:42

### GMAT Club Daily Prep

#### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# The figure above shows a streetlight that consists of a

Author Message
TAGS:

### Hide Tags

Senior Manager
Joined: 31 Oct 2011
Posts: 325
The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

21 Feb 2012, 03:01
13
This post was
BOOKMARKED
00:00

Difficulty:

95% (hard)

Question Stats:

37% (02:12) correct 63% (00:59) wrong based on 251 sessions

### HideShow timer Statistics

The figure above shows a streetlight that consists of a glass sphere, with center O, placed on top of a vertical pole that is 4 meters high. What is the height QR of the streetlight?

(1) The radius of the pole is 6 centimeters.

(2) The radius OQ of the sphere is 24 centimeters.
[Reveal] Spoiler: OA

Attachments

IMG_0413.jpg [ 1.8 MiB | Viewed 4056 times ]

Math Expert
Joined: 02 Sep 2009
Posts: 39622
Re: PT #3 DS 6 [#permalink]

### Show Tags

21 Feb 2012, 03:24
1
KUDOS
Expert's post
eybrj2 wrote:
The figure above shows a streetlight that consists of a glass sphere, with center O, placed on top of a vertical pole that is 4 meters high. What is the height QR of the streetlight?

(1) The radius of the pole is 6 centimeters.

(2) The radius OQ of the sphere is 24 centimeters.

There is absolutely no need to actually calculate the height QR. Just notice that the height of a pole (given) and the radius of the pole completely defines (fixes) it. The same way the radius of a sphere completely defines (fixes) it. So, only if we have defined (fixed) pole and defined (fixed) sphere we can be able to say how much below the top of the pole the sphere goes, and we'll be able to calculate QR.

Both statements together provide us with the info needed: the radius of the pole and the radius of the sphere. Hence when taken together statements are sufficient.

P.S. When dealing with DS problems try to avoid calculations as much as possible. Remember DS problems do not ask you to solve, but rather to determine if you are ABLE to solve and in many cases you can determine that a statement is sufficient without working out all of the math.

Hope it's clear.
_________________
Senior Manager
Status: May The Force Be With Me (D-DAY 15 May 2012)
Joined: 06 Jan 2012
Posts: 278
Location: India
Concentration: General Management, Entrepreneurship
Re: PT #3 DS 6 [#permalink]

### Show Tags

21 Feb 2012, 05:12
Bunuel wrote:
eybrj2 wrote:
The figure above shows a streetlight that consists of a glass sphere, with center O, placed on top of a vertical pole that is 4 meters high. What is the height QR of the streetlight?

(1) The radius of the pole is 6 centimeters.

(2) The radius OQ of the sphere is 24 centimeters.

There is absolutely no need to actually calculate the height QR. Just notice that the height of a pole (given) and the radius of the pole completely defines (fixes) it. The same way the radius of a sphere completely defines (fixes) it. So, only if we have defined (fixed) pole and defined (fixed) sphere we can be able to say how much below the top of the pole the sphere goes, and we'll be able to calculate QR.

Both statements together provide us with the info needed: the radius of the pole and the radius of the sphere. Hence when taken together statements are sufficient.

P.S. When dealing with DS problems try to avoid calculations as much as possible. Remember DS problems do not ask you to solve, but rather to determine if you are ABLE to solve and in many cases you can determine that a statement is sufficient without working out all of the math.

Hope it's clear.

Hi Bunuel,

I'm slightly confused with why do we need the radius of the pole ?

If the sphere sits on the pole its one point would touch the pole, hence the height of street lamp would be pole height + sphere diameter

Thus B should be sufficient correct?

_________________

Giving +1 kudos is a better way of saying 'Thank You'.

Math Expert
Joined: 02 Sep 2009
Posts: 39622
Re: PT #3 DS 6 [#permalink]

### Show Tags

21 Feb 2012, 05:19
boomtangboy wrote:
Bunuel wrote:
eybrj2 wrote:
The figure above shows a streetlight that consists of a glass sphere, with center O, placed on top of a vertical pole that is 4 meters high. What is the height QR of the streetlight?

(1) The radius of the pole is 6 centimeters.

(2) The radius OQ of the sphere is 24 centimeters.

There is absolutely no need to actually calculate the height QR. Just notice that the height of a pole (given) and the radius of the pole completely defines (fixes) it. The same way the radius of a sphere completely defines (fixes) it. So, only if we have defined (fixed) pole and defined (fixed) sphere we can be able to say how much below the top of the pole the sphere goes, and we'll be able to calculate QR.

Both statements together provide us with the info needed: the radius of the pole and the radius of the sphere. Hence when taken together statements are sufficient.

P.S. When dealing with DS problems try to avoid calculations as much as possible. Remember DS problems do not ask you to solve, but rather to determine if you are ABLE to solve and in many cases you can determine that a statement is sufficient without working out all of the math.

Hope it's clear.

Hi Bunuel,

I'm slightly confused with why do we need the radius of the pole ?

If the sphere sits on the pole its one point would touch the pole, hence the height of street lamp would be pole height + sphere diameter

Thus B should be sufficient correct?

No, it does't "sit" on the pole it's placed IN the circular top of the pole (notice that the sphere is slightly below the top of the pole). Now, consider extreme case when the radius of the pole is more than the radius of the sphere, in that case the sphere will just fall into it.

Hope it's clear.
_________________
Senior Manager
Status: May The Force Be With Me (D-DAY 15 May 2012)
Joined: 06 Jan 2012
Posts: 278
Location: India
Concentration: General Management, Entrepreneurship
Re: The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

21 Feb 2012, 23:39
Hi Bunuel,

Thanks for your reply but I have this question, may be its even silly but in your reply you assumed the pole to be hollow i.e a steel pipe but the question says pole i.e solid pole like a vaulting pole hence the chance of the sphere going into the pole is nil.

I dont know how the GMAT defines such terms cause both possibilities exist
_________________

Giving +1 kudos is a better way of saying 'Thank You'.

Math Expert
Joined: 02 Sep 2009
Posts: 39622
Re: The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

21 Feb 2012, 23:42
boomtangboy wrote:
Hi Bunuel,

Thanks for your reply but I have this question, may be its even silly but in your reply you assumed the pole to be hollow i.e a steel pipe but the question says pole i.e solid pole like a vaulting pole hence the chance of the sphere going into the pole is nil.

I dont know how the GMAT defines such terms cause both possibilities exist

Notice that the sphere is slightly below the top of the pole.
_________________
Senior Manager
Joined: 31 Oct 2011
Posts: 325
Re: The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

24 Feb 2012, 03:32
I was also confused the part that boomtangboy mentioned above.

Bunuel says that the sphere slightly goes into the pole in the picture, but should we solve the problem with the information in the Q, not the picture. The question doesn't say that the sphere slightly goes into the pole.

So confusing....
Math Expert
Joined: 02 Sep 2009
Posts: 39622
Re: The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

24 Feb 2012, 03:46
eybrj2 wrote:
I was also confused the part that boomtangboy mentioned above.

Bunuel says that the sphere slightly goes into the pole in the picture, but should we solve the problem with the information in the Q, not the picture. The question doesn't say that the sphere slightly goes into the pole.

So confusing....

But the question doesn't say the opposite either: why are you assuming that the sphere and the pole have only one tangent point?

In addition if it were the case then the whole point of the drawing and the radius of the pole makes little sense, because the question just becomes about adding two quantities: length of the pole and the diameter of the sphere.
_________________
Moderator
Joined: 01 Sep 2010
Posts: 3211
Re: The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

29 Feb 2012, 02:23
Only with what Bunuel says we have the answer C, whereas if the two figures touch each other in one point the solution was D, but when I look at this kind of statement I think that something is behind the scenes.

Too simple a question like this to say: we have the radi x 2 + height ...........this is not wonderland, this is Mordor Land.
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15929
Re: The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

02 Feb 2014, 07:04
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Manager
Status: Please do not forget to give kudos if you like my post
Joined: 19 Sep 2008
Posts: 122
Location: United States (CA)
The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

18 Oct 2014, 13:38
2
This post was
BOOKMARKED
See that attached picture. We need both radius of the glass sphere and the pole in order to calculate the total height of the combined structure.

eybrj2 wrote:
The figure above shows a streetlight that consists of a glass sphere, with center O, placed on top of a vertical pole that is 4 meters high. What is the height QR of the streetlight?

(1) The radius of the pole is 6 centimeters.

(2) The radius OQ of the sphere is 24 centimeters.

Attachments

Screen Shot 2014-11-03 at 8.14.08 PM.png [ 180.16 KiB | Viewed 2078 times ]

_________________

[Reveal] Spoiler:

Last edited by pradeepss on 03 Nov 2014, 21:22, edited 2 times in total.
Intern
Joined: 05 Sep 2014
Posts: 8
Re: The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

27 Oct 2014, 11:51
I am still confused how the information is sufficient.

How do we calculate the c shown above? We only know that a is 6. What is the value of b?
Intern
Joined: 05 Sep 2014
Posts: 8
Re: The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

02 Nov 2014, 17:11
Bunnel, can you help me?
Manager
Status: Please do not forget to give kudos if you like my post
Joined: 19 Sep 2008
Posts: 122
Location: United States (CA)
The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

03 Nov 2014, 21:22
1
KUDOS
i updated the picture...please take a look.

basically, we know that radius of pole is 6 and radius of the sphere is 24. so we can calculate the partial portion part of the radius of sphere. We can then find the needed information.

hope this helps.

annie2014 wrote:
I am still confused how the information is sufficient.

How do we calculate the c shown above? We only know that a is 6. What is the value of b?

_________________

[Reveal] Spoiler:

GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15929
Re: The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

21 May 2016, 10:07
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15929
Re: The figure above shows a streetlight that consists of a [#permalink]

### Show Tags

27 May 2017, 15:03
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: The figure above shows a streetlight that consists of a   [#permalink] 27 May 2017, 15:03
Similar topics Replies Last post
Similar
Topics:
4 The figure above shows the dimensions of a square picture frame that 5 22 Dec 2014, 08:11
1 The figure above shows the shape of a flowerbed. If arcs WZ 3 16 Oct 2016, 18:14
17 The figure above shows a construction plan for the intersect 15 27 Mar 2017, 11:16
5 The figure above shows the number of meters in the lengths 3 21 Jan 2016, 08:28
20 The figure above shows the present position on a radar 22 24 Jul 2016, 06:41
Display posts from previous: Sort by