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how to solve this question

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how to solve this question

by zareentaj » Mon Aug 09, 2010 9:17 pm
The centre of circle which touch the y-axis at (0,3) and making an intercept of 2 units on the positive x-axis, is:
(a) (10,sqrt{3})
(b) (sqrt{3},10)
(c) (sqrt{10},3)
(d) (3,sqrt{10})

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by kvcpk » Mon Aug 09, 2010 9:25 pm
zareentaj wrote:The centre of circle which touch the y-axis at (0,3) and making an intercept of 2 units on the positive x-axis, is:
(a) (10,sqrt{3})
(b) (sqrt{3},10)
(c) (sqrt{10},3)
(d) (3,sqrt{10})
It is given that the circle touches the y-axes at (0,3)
Which means y-axis is perpendicular to the line drawn from centre to (0,3)

This means that y-coordinate of the centre will be 3.

pick C

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by 4GMAT_Mumbai » Mon Aug 09, 2010 9:31 pm
KVCPK ... That was my initial approach too ... But, distance of OA is not equal to OB assuming that A is (0.3) and B is (2,0) ... Hence, I suppose c is not the answer ..
Naveenan Ramachandran
4GMAT, Dadar(W) & Ghatkopar(W), Mumbai

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by zareentaj » Mon Aug 09, 2010 10:10 pm
kvcpk wrote:
zareentaj wrote:The centre of circle which touch the y-axis at (0,3) and making an intercept of 2 units on the positive x-axis, is:
(a) (10,sqrt{3})
(b) (sqrt{3},10)
(c) (sqrt{10},3)
(d) (3,sqrt{10})
It is given that the circle touches the y-axes at (0,3)
Which means y-axis is perpendicular to the line drawn from centre to (0,3)

This means that y-coordinate of the centre will be 3.

pick C
Thanks, give explanation...

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by kvcpk » Mon Aug 09, 2010 10:30 pm
4GMAT_Mumbai wrote:KVCPK ... That was my initial approach too ... But, distance of OA is not equal to OB assuming that A is (0.3) and B is (2,0) ... Hence, I suppose c is not the answer ..
Yeah you are right. I see what you are saying. But I dont see any option satisfying this.

Moreover, I have a logical query with this question. Any number of circles can be drawn passing through 2 points. How can there be a single centre?
May be the question is missing something.