Last visit was: 20 Nov 2025, 02:14 It is currently 20 Nov 2025, 02:14
Close
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
Your Progress

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
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Close
Request Expert Reply
Confirm Cancel
User avatar
christoph
Joined: 30 Sep 2004
Last visit: 23 Nov 2011
Posts: 684
Own Kudos:
1,569
 [131]
Location: Germany
Posts: 684
Kudos: 1,569
 [131]
12
Kudos
Add Kudos
118
Bookmarks
Bookmark this Post
Most Helpful Reply
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 20 Nov 2025
Posts: 105,408
Own Kudos:
Given Kudos: 99,987
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 105,408
Kudos: 778,448
 [70]
39
Kudos
Add Kudos
31
Bookmarks
Bookmark this Post
User avatar
KarishmaB
Joined: 16 Oct 2010
Last visit: 19 Nov 2025
Posts: 16,267
Own Kudos:
77,001
 [20]
Given Kudos: 482
Location: Pune, India
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 16,267
Kudos: 77,001
 [20]
17
Kudos
Add Kudos
3
Bookmarks
Bookmark this Post
General Discussion
User avatar
banerjeea_98
Joined: 18 Nov 2004
Last visit: 17 May 2012
Posts: 676
Own Kudos:
201
 [2]
Posts: 676
Kudos: 201
 [2]
2
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I think it's "B".

For the circle to intersect, we have to have a center which is 4 units or < away from the y axis as 4 is the radius of this circle.

I. a2+b2 > 16.....a = 3, b = 8, circle intersect, if a = 5 and b = 0, it doesn't....insuff

II. a = |b|+5.....means that x coordinate of center is always +ve and >=5.....any center with >=5 as X coordinate will never intersect Y axis as the circle radius is 4....suff
User avatar
nocilis
Joined: 19 Nov 2004
Last visit: 11 Jul 2008
Posts: 274
Own Kudos:
1,539
 [13]
Location: SF Bay Area, USA
Posts: 274
Kudos: 1,539
 [13]
10
Kudos
Add Kudos
3
Bookmarks
Bookmark this Post
Another way of doing this:
(x-a)^2 + (y-b)^2=16 intersect the y-axis when x=0

=> a^2 + y^2 + b^2 - 2yb =16
or
y^2 -2yb + a^2 + b^2 -16 =0

For this quedratic eqn. to have real roots,
4b^2 - 4(1)(a^2 + b^2 -16) >=0
or a^2 <=16


(1) a^2+b^2>16

It does not say anything about a^2 being <=16. So can't say

(2) a=|b|+5

|b| is postive or zero. So a is atleast 5 and a^2 is atleast 25.
This contradicts our requirement that a^2 <=16. So no, it does not intersect the y axis

B it is.
User avatar
catty2004
Joined: 30 May 2008
Last visit: 01 Nov 2016
Posts: 35
Own Kudos:
Given Kudos: 26
Posts: 35
Kudos: 966
Kudos
Add Kudos
Bookmarks
Bookmark this Post
nocilis
Another way of doing this:
(x-a)^2 + (y-b)^2=16 intersect the y-axis when x=0

=> a^2 + y^2 + b^2 - 2yb =16
or
y^2 -2yb + a^2 + b^2 -16 =0

For this quedratic eqn. to have real roots,
4b^2 - 4(1)(a^2 + b^2 -16) >=0or a^2 <=16


(1) a^2+b^2>16

It does not say anything about a^2 being <=16. So can't say

(2) a=|b|+5

|b| is postive or zero. So a is atleast 5 and a^2 is atleast 25.
This contradicts our requirement that a^2 <=16. So no, it does not intersect the y axis

B it is.


I'm not sure the reasoning behind the red part in bold section......how did you get to 4b^2 - 4(1)(a^2 + b^2 -16) >=0 ?
User avatar
Sachin9
Joined: 22 Jul 2012
Last visit: 25 Dec 2015
Posts: 351
Own Kudos:
Given Kudos: 562
Status:Gonna rock this time!!!
Location: India
GMAT 1: 640 Q43 V34
GMAT 2: 630 Q47 V29
WE:Information Technology (Computer Software)
GMAT 2: 630 Q47 V29
Posts: 351
Kudos: 174
Kudos
Add Kudos
Bookmarks
Bookmark this Post
VeritasPrepKarishma
christoph
Does the curve (x-a)^2 + (y-b)^2=16 intersect the y-axis ?

(1) a^2+b^2>16
(2) a=|b|+5

What do we mean by 'intersect the y axis'? We mean that the x co-ordinate is 0.

So let's put x = 0 and see what we get:
\((0-a)^2 + (y-b)^2 = 16\)
\(y = b + (16 - a^2)^{1/2}\)

Now what decides whether we get a value for y or not? Obviously, if \((16 - a^2)\) is negative, y will have no real value and the curve will not intersect the y axis. If instead \((16 - a^2)\) is 0 or positive, the curve will intersect the y axis. So we can answer the question asked if we know whether \((16 - a^2)\) is positive/0 or not.

Is \((16 - a^2) >= 0\)
or Is \((a^2 - 16) <= 0\)
Is \(-4 <= a <= 4\)?

We have simplified the question stem as much as we could. Let's go on to the given statements.

(1) \(a^2+b^2>16\)
Doesn't tell us about the value of a. a could be 2 or 10 or many other values.

(2) a=|b|+5
a is 5 or greater since |b| is at least 0. This tells us that 'a' does not lie between -4 and 4. Hence this statement is sufficient to answer the question.

Answer (B)


Hi Karishma,
What does intersect mean? In our Indian education system , we have learnt that intersection means that the arcs/lines cross each other.
I remember reading in MGMAT forum that on the GMAT intersection would also mean that the line may be a tangent to the arc. .
So in that case, even if |a|=4, then the circle intersects the y axis ..
Is my understanding correct?

Regards,
Sachin
User avatar
KarishmaB
Joined: 16 Oct 2010
Last visit: 19 Nov 2025
Posts: 16,267
Own Kudos:
77,001
 [1]
Given Kudos: 482
Location: Pune, India
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 16,267
Kudos: 77,001
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Sachin9



Hi Karishma,
What does intersect mean? In our Indian education system , we have learnt that intersection means that the arcs/lines cross each other.
I remember reading in MGMAT forum that on the GMAT intersection would also mean that the line may be a tangent to the arc. .
So in that case, even if |a|=4, then the circle intersects the y axis ..
Is my understanding correct?

Regards,
Sachin

Yes, intersect (as far as GMAT is concerned) means touch. x co-ordinate is 0 there. Where do the lines/curves go after touching is immaterial. Notice that in the explanation above, I have given:
"If instead (16 - a^2) is 0 or positive, the curve will intersect the y axis."

It means that even if a = 4, the curve will intersect the y axis.
User avatar
mau5
User avatar
Verbal Forum Moderator
Joined: 10 Oct 2012
Last visit: 31 Dec 2024
Posts: 479
Own Kudos:
3,340
 [1]
Given Kudos: 141
Posts: 479
Kudos: 3,340
 [1]
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
From the given problem, we will have the curve intersect the y-axis iff we get a real value for the given curve at x=0.

Thus, putting x=0, we get

\((-a)^2+(y-b)^2 = 16\)

\(or (y-b)^2 = 16-a^2\)

Now for real value of y, we have to have \(16-a^2>=0.\)

\(or a^2<=16\)

\(-4<=a<=4.\)

F.S 1 not sufficient.

F.S 2, as a= mod(b)+5, the minimum value of a has to be 5. Thus sufficient. The curve will not intersect the y-axis.

B.
avatar
dyuthi92
Joined: 01 May 2013
Last visit: 19 Apr 2014
Posts: 2
Given Kudos: 12
Posts: 2
Kudos: 0
Kudos
Add Kudos
Bookmarks
Bookmark this Post
banerjeea_98
I think it's "B".

For the circle to intersect, we have to have a center which is 4 units or < away from the y axis as 4 is the radius of this circle.

I. a2+b2 > 16.....a = 3, b = 8, circle intersect, if a = 5 and b = 0, it doesn't....insuff

II. a = |b|+5.....means that x coordinate of center is always +ve and >=5.....any center with >=5 as X coordinate will never intersect Y axis as the circle radius is 4....suff

what if b is less than zero.
as we know |x| = x if x <0 and |x| = -x if x >0.
in this case we get two equations for a 1) a-b = 5( a could be 9 and be could be 4.
second equation for a is a+b = 5 (then b=0 and a=5 or a=5 and b=0 or a=1 and b =4..)could be possibilities if a=5.it say it does intersect y axis but in all the other three cases it intersects with y axis.in this way i got E. please tell me if am missing something.
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 20 Nov 2025
Posts: 105,408
Own Kudos:
Given Kudos: 99,987
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 105,408
Kudos: 778,448
Kudos
Add Kudos
Bookmarks
Bookmark this Post
dyuthi92
banerjeea_98
I think it's "B".

For the circle to intersect, we have to have a center which is 4 units or < away from the y axis as 4 is the radius of this circle.

I. a2+b2 > 16.....a = 3, b = 8, circle intersect, if a = 5 and b = 0, it doesn't....insuff

II. a = |b|+5.....means that x coordinate of center is always +ve and >=5.....any center with >=5 as X coordinate will never intersect Y axis as the circle radius is 4....suff

what if b is less than zero.
as we know |x| = x if x <0 and |x| = -x if x >0.
in this case we get two equations for a 1) a-b = 5( a could be 9 and be could be 4.
second equation for a is a+b = 5 (then b=0 and a=5 or a=5 and b=0 or a=1 and b =4..)could be possibilities if a=5.it say it does intersect y axis but in all the other three cases it intersects with y axis.in this way i got E. please tell me if am missing something.

If b<0, for example, if b=-1, then still \(a = |b| + 5=6>4\).

Check here: does-the-curve-x-a-2-y-b-2-16-intersect-the-y-axis-14046.html#p1072781 or here: does-the-curve-x-a-2-y-b-2-16-intersect-the-y-axis-14046.html#p1073168

Hope it helps.
avatar
krrish
Joined: 04 Mar 2013
Last visit: 03 Feb 2014
Posts: 46
Own Kudos:
Given Kudos: 6
Location: India
Concentration: General Management, Marketing
GPA: 3.49
WE:Web Development (Computer Software)
Posts: 46
Kudos: 15
Kudos
Add Kudos
Bookmarks
Bookmark this Post
christoph
Does the curve (x-a)^2 + (y-b)^2=16 intersect the y-axis ?

(1) a^2+b^2>16
(2) a=|b|+5

s1: put a= 0 and b =5 then the cirlce touches y axis but if the center is 3, 8 then the cirlce never touches y axis so, not sufficient :)

s2: this clearly shows, a is not equat to 0 so, it never touches y axis so sufficient.

but took more than 2 minutes to solve :( :(
avatar
manishtank1988
Joined: 14 Oct 2012
Last visit: 31 Oct 2019
Posts: 114
Own Kudos:
Given Kudos: 1,023
Products:
Posts: 114
Kudos: 282
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hello Friends,
I would like to clarify 1 point which wasn't clear to me:
Bunuel "Now, if a, the x-coordinate of the center, is more than 4 or less than -4 then the radius of the circle, which is 4, won't be enough for curve to intersect with Y axis. So basically the question asks whether |a|>4: if it is, then the answer will be NO: the curve does not intersect with Y axis and if it's not, then the answer will be YES: the curve intersects with Y axis."
Here's why:
Equation: (x-a)^2 + (y-b)^2 = 16
Let a = b = 5 and we are trying to find y intercept => x = 0
25 + (y-5)^2 = 16
y^2 - 10y + 25 + 9 = 0
y^2 - 10y + 34 = 0
b^2 - 4ac = 100 - 4*(1)*(34) = 100 - 136 = -36
delta < 0 => NO solution. Thus curve [ y^2 - 10y + 34 = 0 ] doesn't intersect y-axis.
This sort of makes sense from the diagram as x co-ordinate of the center determines the distance of center of circle from y-axis and y co-ordinate decides the distance of center of circle from x-axis.


Summary:
In (x-a)^2 + (y-b)^2 = c^2 if:
(i) |a| > c => This distance of center of circle from y-axis is MORE THAN the radius. So no point of intersection between circle and Y-axis.
(ii) |b| > c => This distance of center of circle from x-axis is MORE THAN the radius. So no point of intersection between circle and x-axis.
avatar
ayas7
Joined: 29 Sep 2017
Last visit: 06 Nov 2017
Posts: 6
Own Kudos:
Given Kudos: 19
Posts: 6
Kudos: 1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
nocilis
Another way of doing this:
(x-a)^2 + (y-b)^2=16 intersect the y-axis when x=0

=> a^2 + y^2 + b^2 - 2yb =16
or
y^2 -2yb + a^2 + b^2 -16 =0

For this quedratic eqn. to have real roots,
4b^2 - 4(1)(a^2 + b^2 -16) >=0
or a^2 <=16


(1) a^2+b^2>16

It does not say anything about a^2 being <=16. So can't say

(2) a=|b|+5

|b| is postive or zero. So a is atleast 5 and a^2 is atleast 25.
This contradicts our requirement that a^2 <=16. So no, it does not intersect the y axis

B it is.

Can you explain how you calculated this please?
"For this quedratic eqn. to have real roots,
4b^2 - 4(1)(a^2 + b^2 -16) >=0
or a^2 <=16 "

did you use b^2-4ac?
avatar
ayas7
Joined: 29 Sep 2017
Last visit: 06 Nov 2017
Posts: 6
Own Kudos:
Given Kudos: 19
Posts: 6
Kudos: 1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
VeritasPrepKarishma
christoph
Does the curve (x-a)^2 + (y-b)^2=16 intersect the y-axis ?

(1) a^2+b^2>16
(2) a=|b|+5

What do we mean by 'intersect the y axis'? We mean that the x co-ordinate is 0.

So let's put x = 0 and see what we get:
\((0-a)^2 + (y-b)^2 = 16\)
\(y = b + (16 - a^2)^{1/2}\)

Now what decides whether we get a value for y or not? Obviously, if \((16 - a^2)\) is negative, y will have no real value and the curve will not intersect the y axis. If instead \((16 - a^2)\) is 0 or positive, the curve will intersect the y axis. So we can answer the question asked if we know whether \((16 - a^2)\) is positive/0 or not.

Is \((16 - a^2) >= 0\)
or Is \((a^2 - 16) <= 0\)
Is \(-4 <= a <= 4\)?

We have simplified the question stem as much as we could. Let's go on to the given statements.

(1) \(a^2+b^2>16\)
Doesn't tell us about the value of a. a could be 2 or 10 or many other values.

(2) a=|b|+5
a is 5 or greater since |b| is at least 0. This tells us that 'a' does not lie between -4 and 4. Hence this statement is sufficient to answer the question.

Answer (B)

can you please share the steps of simplification with: (0−a)2+(y−b)2=16(0−a)2+(y−b)2=16
y=b+(16−a2)1/2?

thank you!
User avatar
KarishmaB
Joined: 16 Oct 2010
Last visit: 19 Nov 2025
Posts: 16,267
Own Kudos:
77,001
 [1]
Given Kudos: 482
Location: Pune, India
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 16,267
Kudos: 77,001
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
ayas7
VeritasPrepKarishma
christoph
Does the curve (x-a)^2 + (y-b)^2=16 intersect the y-axis ?

(1) a^2+b^2>16
(2) a=|b|+5

What do we mean by 'intersect the y axis'? We mean that the x co-ordinate is 0.

So let's put x = 0 and see what we get:
\((0-a)^2 + (y-b)^2 = 16\)
\(y = b + (16 - a^2)^{1/2}\)

Now what decides whether we get a value for y or not? Obviously, if \((16 - a^2)\) is negative, y will have no real value and the curve will not intersect the y axis. If instead \((16 - a^2)\) is 0 or positive, the curve will intersect the y axis. So we can answer the question asked if we know whether \((16 - a^2)\) is positive/0 or not.

Is \((16 - a^2) >= 0\)
or Is \((a^2 - 16) <= 0\)
Is \(-4 <= a <= 4\)?

We have simplified the question stem as much as we could. Let's go on to the given statements.

(1) \(a^2+b^2>16\)
Doesn't tell us about the value of a. a could be 2 or 10 or many other values.

(2) a=|b|+5
a is 5 or greater since |b| is at least 0. This tells us that 'a' does not lie between -4 and 4. Hence this statement is sufficient to answer the question.

Answer (B)

can you please share the steps of simplification with: (0−a)2+(y−b)2=16(0−a)2+(y−b)2=16
y=b+(16−a2)1/2?

thank you!


So let's put x = 0 and see what we get:
\((0-a)^2 + (y-b)^2 = 16\)
\(a^2 + (y - b)^2 = 16\)
\((y - b)^2 = 16 - a^2\)
\((y - b) = \sqrt{16 - a^2}\)
\(y = b + \sqrt{16 - a^2}\)
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 38,595
Own Kudos:
Posts: 38,595
Kudos: 1,079
Kudos
Add Kudos
Bookmarks
Bookmark this Post
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.
Moderators:
Math Expert
105408 posts
496 posts