Circles...Radius problem...??

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nroy347: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Mon Apr 02, 2012 9:53 am

Circles...Radius problem...??

by nroy347 » Mon Aug 27, 2012 12:04 pm

In the xy-plane, the point (-2, -3) is the center of a circle. The point (-2, 1) lies inside the circle and the point (4, -3) lies outside the circle. If the radius r of the circle is an integer, then r =
[A] 6
5
[C] 4
[D] 3
[E] 2

Please temme how to approach...

Quote

Source: Beat The GMAT — Problem Solving | Mon Aug 27, 2012 12:04 pm

vk_vinayak: Legendary Member; Posts: 502; Joined: Tue Jun 03, 2008 11:36 pm; Thanked: 99 times; Followed by:21 members

by vk_vinayak » Mon Aug 27, 2012 12:09 pm

nroy347 wrote:In the xy-plane, the point (-2, -3) is the center of a circle. The point (-2, 1) lies inside the circle and the point (4, -3) lies outside the circle. If the radius r of the circle is an integer, then r =
[A] 6
5
[C] 4
[D] 3
[E] 2

Please temme how to approach...

Draw a X Y co-ordinate. And see the difference between center and each point.

The point (-2, 1) lies inside the circle => radius is greater than 4
the point (4, -3) lies outside the circle => radius is less than 6.

Ans is B.

- VK

I will (Learn. Recognize. Apply)

Quote

cypherskull: Senior | Next Rank: 100 Posts; Posts: 94; Joined: Sat Mar 31, 2012 3:39 am; Location: Calcutta; Thanked: 8 times

by cypherskull » Mon Aug 27, 2012 12:26 pm

Calculate the distance b/w (-2,-3) and (-2,1); d = 4.
Since (-2,1) is inside the circle, r > 4. Eliminate C,D,E.

Calculate the distance b/w (-2,-3) and (4,-3); d = 6.
Since (4,-3) is outside the circle, r < 6. Eliminate A. [spoiler]Ans:B[/spoiler]

Regards,
Sunit

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