It is currently 07 Dec 2019, 16:25

### 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

# In the xy-plane, C and D are circles centered at the origin

Author Message
TAGS:
Founder
Joined: 18 Apr 2015
Posts: 8961
Followers: 178

Kudos [?]: 2116 [0], given: 8305

In the xy-plane, C and D are circles centered at the origin [#permalink]  29 Nov 2019, 02:35
Expert's post
00:00

Question Stats:

43% (01:36) correct 56% (00:26) wrong based on 16 sessions
In the xy-plane, $$C$$ and $$D$$ are circles centered at the origin with radii $$\sqrt{17}$$ and $$\sqrt{5}$$, respectively.

 Quantity A Quantity B The number of points (a, b) on circle $$C$$ where both a and b are integers The number of points (a, b) on circle $$D$$ where both a and b are integers

A)The quantity in Column A is greater.
B)The quantity in Column B is greater.
C)The two quantities are equal.
D)The relationship cannot be determined from the information given.

Kudos for the right answer and explanation
[Reveal] Spoiler: OA

_________________

Need Practice? 20 Free GRE Quant Tests available for free with 20 Kudos
GRE Prep Club Members of the Month: Each member of the month will get three months free access of GRE Prep Club tests.

Intern
Joined: 05 Oct 2019
Posts: 26
Followers: 0

Kudos [?]: 24 [1] , given: 15

Re: In the xy-plane, C and D are circles centered at the origin [#permalink]  29 Nov 2019, 18:33
1
KUDOS
Equation of circle C: x2 + y2 = 17
Equation of circle D: x2 + y2 = 5

The question can now be rephrased as: number of integer pairs of (x,y) that satisfy above equations
For circle C, you have (4,1) and its 3 other variants by interchanging the -ve sign - (4,1),(4,-1),(-4,1),(-4,-1). Similar pattern of roots by interchanging x & y. - 4 more i.e. (1,4),(1,-4),(-1,4),(-1,-4)
For circle D, as well 8 roots obtained by interchanging signs & positions of (2,1)

Thus option C
Re: In the xy-plane, C and D are circles centered at the origin   [#permalink] 29 Nov 2019, 18:33
Display posts from previous: Sort by