GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 16 Dec 2018, 04:51

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 December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
• FREE Quant Workshop by e-GMAT!

December 16, 2018

December 16, 2018

07:00 AM PST

09:00 AM PST

Get personalized insights on how to achieve your Target Quant Score.
• Free GMAT Prep Hour

December 16, 2018

December 16, 2018

03:00 PM EST

04:00 PM EST

Strategies and techniques for approaching featured GMAT topics

The circumference of circle X is 1/2 the circumference of circle Y. Wh

Author Message
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 51223
The circumference of circle X is 1/2 the circumference of circle Y. Wh  [#permalink]

Show Tags

13 Apr 2018, 00:26
00:00

Difficulty:

15% (low)

Question Stats:

89% (00:57) correct 11% (01:12) wrong based on 41 sessions

HideShow timer Statistics

The circumference of circle X is 1/2 the circumference of circle Y. What is the area of circle X?

(1) The area of circle Y is $$100\pi$$ ft^2.
(2) The circumference of circle Y is $$20\pi$$ ft

_________________
PS Forum Moderator
Status: It always seems impossible until it's done.
Joined: 16 Sep 2016
Posts: 425
GMAT 1: 740 Q50 V40
Re: The circumference of circle X is 1/2 the circumference of circle Y. Wh  [#permalink]

Show Tags

13 Apr 2018, 00:39
Bunuel wrote:
The circumference of circle X is 1/2 the circumference of circle Y. What is the area of circle X?

(1) The area of circle Y is $$100\pi$$ ft^2.
(2) The circumference of circle Y is $$20\pi$$ ft

Since we know the relationship between R1 and R2 of the two circles..

2*pi*R2 = 0.5 * 2*pi*R1

Anything that gives R1 will give us R2.

Hence option (D) is our answer without solving for the actual values of anything.

Best,

Posted from my mobile device
Intern
Joined: 31 Jul 2017
Posts: 11
Re: The circumference of circle X is 1/2 the circumference of circle Y. Wh  [#permalink]

Show Tags

13 Apr 2018, 02:15
1 stmt gives 2 output
2 stmt gives correct radius which will be calcuated for Area of Circle X
Math Expert
Joined: 02 Aug 2009
Posts: 7108
Re: The circumference of circle X is 1/2 the circumference of circle Y. Wh  [#permalink]

Show Tags

13 Apr 2018, 02:18
1
rohitf23 wrote:
1 stmt gives 2 output
2 stmt gives correct radius which will be calcuated for Area of Circle X

Yes statement 1 gives two output ..$$r^2 = 100...$$ r = 10 or -10
But we are looking at radius and it cannot be NEGATIVE so r = 10
suff
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

GMAT online Tutor

Intern
Joined: 10 Jan 2017
Posts: 7
Location: India
Concentration: Social Entrepreneurship, General Management
WE: Information Technology (Computer Software)
Re: The circumference of circle X is 1/2 the circumference of circle Y. Wh  [#permalink]

Show Tags

13 Apr 2018, 04:40
1
Cx = 2 pi r
Cy = pi r

Statement 1
Ay=100 pi
also, Ay=C^2/4 pi ==> 100 pi = pi^2 r^2/4 pi ==>r = +/- 20, but radius will be positive so r=20

Statement 2

gives us the same info as statement 1

Cy=20 pi = pi r ==> r=20

Therefore ans is D
Director
Joined: 02 Oct 2017
Posts: 728
Re: The circumference of circle X is 1/2 the circumference of circle Y. Wh  [#permalink]

Show Tags

27 Apr 2018, 21:50
2πx=(1/2)*2πy
X=y/2

1) get value of y using πr^2
Then calculate x
Sufficient

II)get value of y using 2πr
Then calculate x
Sufficient

Posted from my mobile device
_________________

Give kudos if you like the post

Re: The circumference of circle X is 1/2 the circumference of circle Y. Wh &nbs [#permalink] 27 Apr 2018, 21:50
Display posts from previous: Sort by