Last visit was: 24 Apr 2024, 01:36 It is currently 24 Apr 2024, 01:36

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
SORT BY:
Date
Tags:
Show Tags
Hide Tags
User avatar
Intern
Intern
Joined: 09 Sep 2010
Posts: 8
Own Kudos [?]: 35 [33]
Given Kudos: 11
Send PM
Most Helpful Reply
Math Expert
Joined: 02 Sep 2009
Posts: 92900
Own Kudos [?]: 618671 [20]
Given Kudos: 81586
Send PM
General Discussion
User avatar
Retired Moderator
Joined: 20 Dec 2010
Posts: 1114
Own Kudos [?]: 4702 [2]
Given Kudos: 376
Send PM
User avatar
Intern
Intern
Joined: 09 Sep 2010
Posts: 8
Own Kudos [?]: 35 [0]
Given Kudos: 11
Send PM
Re: Co-ordinate Geometry- Area of a Triangle [#permalink]
I was stuck at understanding Statement (1) for a long time. That diagram really clears my doubt. Thanks guys :)
Manager
Manager
Joined: 16 May 2011
Posts: 240
Own Kudos [?]: 308 [1]
Given Kudos: 64
Concentration: Finance, Real Estate
GMAT Date: 12-27-2011
WE:Law (Law)
Send PM
Re: Co-ordinate Geometry- Area of a Triangle [#permalink]
1
Bookmarks
another simple and straightforward from Bunuel. must admit, i enjoy reading your posts.
User avatar
Manager
Manager
Joined: 03 Aug 2010
Status:And the Prep starts again...
Posts: 84
Own Kudos [?]: 259 [0]
Given Kudos: 20
Concentration: IT Consulting
GMAT 2: 520
Send PM
Re: Vertices of a traingle are at (-2,1) , (3,1) & (x,y) on a [#permalink]
Bunuel you genius... :-) Best explanation as always.
User avatar
Manager
Manager
Joined: 12 Feb 2012
Posts: 105
Own Kudos [?]: 216 [0]
Given Kudos: 28
Send PM
If vertices of a triangle have coordinates [#permalink]
swatirpr wrote:
If vertices of a triangle have coordinates \((-2, 2), (3, 2), (x, y)\) , what is the area of the triangle?

1. \(|y - 2| = 1\)
2. angle at the vertex \((x, y)\) equals 90 degrees


Sorry to revive this old post.

So 1. \(|y - 2| = 1\) ===>\(y-2=1\)or\(y-2=-1\) ===> two solutions \(y=1\) or\(y=3\). Notice that that regardless of what value of x, the base will always be the distance between \((-2, 2) and (3, 2)\) and the height will always be 1. Therefore the area will always be the same.

2) We know the base and that the third vertex will form a right angle. Well if that is the case, the only right angles that can formed for a given line is one in which it is the diameter of a circle. The third point on this line will always form a right angled triangle. All right angled triangles have their hypotenuse as the diameter of a circle and the third vertex a point on the circle. As you can see, while we know that this third, unknown, vertex will be on this circle, we dont't know where. Therefore the right triangle will have different areas as the third point glides across the circle. The area will reach a maximum when the point forms a isoclese right triangle.
Attachments

gmat_delete2.PNG
gmat_delete2.PNG [ 10.16 KiB | Viewed 11946 times ]

gmat_delete.PNG
gmat_delete.PNG [ 8.9 KiB | Viewed 11962 times ]

avatar
Intern
Intern
Joined: 06 Apr 2011
Posts: 10
Own Kudos [?]: 9 [0]
Given Kudos: 292
Send PM
Re: Vertices of a traingle are at (-2,1) , (3,1) & (x,y) on a [#permalink]
Bunuel that was a simply marvelous
No need for any calculations to solve the question
User avatar
Intern
Intern
Joined: 15 Jul 2012
Posts: 24
Own Kudos [?]: 43 [0]
Given Kudos: 245
Send PM
Vertices of a traingle are at (-2,1) , (3,1) & (x,y) on a [#permalink]
Bunuel wrote:
sandhyash wrote:
Q - Vertices of a traingle are at (-2,1) , (3,1) & (x,y) on a coordinate plane. What is the area of the triangle ?

1) |y-1| =1
2) Angle at Vertex (x,y) = 90 degrees

Source : MGMAT Test

Solution given : (A)

The explanation given in the solution is that :

From Statement (1) either y=0 or y=2, either way base is 5 and height =1. Hence area can be computed

Statement (2) is not enough


I did not understand this explanation. Please help !! Thanks in advance.


Below is almost identical question:

Vertices of a triangle have coordinates (-2, 2), (3, 2), (x, y). What is the area of the triangle?

(1) |y - 2| = 1
(2) angle at the vertex \((x, y)\) equals 90 degrees

Given two points A(-2,2) and B(3,2). Question: Area ABC=?, where C(x,y).

(1) |y-2|=1 --> \(y=3\) or \(y=1\) --> vertex C could be anywhere on the blue line \(y=3\) or anywhere on the red line \(y=1\). But in ANY case the are of ABC will be the same --> \(area=\frac{1}{2}*base*height\) so \(base=AB=5\) and the height would be 1 for any point C (see two possible locations of C: C1 and C2, the heights of ABC1 and ABC2 are the same and equal to 1) --> \(area=\frac{1}{2}*base*height=\frac{5}{2}\). Sufficient.

(2) angle at the vertex C(x,y) equals to 90 degrees --> ABC is a right triangle with hypotenuse AB --> consider AB to be diameter of a circle and in this case C could be anywhere on the circle and it will be right angle (if the diameter of the circle is also the inscribed triangle’s side, then that triangle is a right triangle), thus height of ABC will be different for different location of point C, resulting the different areas (see two possible locations of of C: C3 and C4, heights of ABC3 and ABC4 are different). Not sufficient.

Answer: A.

Hope it heps.



Hey bunuel,
brilliant explanation.

But, i have a silly doubt in this problem. arent we assuming that the base is fixed at (-2, 2), (3, 2). why cant the base be on the unknown point.

from 1st statement we get the value of y as 3 or 1.
why cant the base be on (x,1) and (3,2) or (x,3) and (3,2)?
Math Expert
Joined: 02 Sep 2009
Posts: 92900
Own Kudos [?]: 618671 [0]
Given Kudos: 81586
Send PM
Vertices of a traingle are at (-2,1) , (3,1) & (x,y) on a [#permalink]
Expert Reply
saggii27 wrote:
Bunuel wrote:
sandhyash wrote:
Q - Vertices of a traingle are at (-2,1) , (3,1) & (x,y) on a coordinate plane. What is the area of the triangle ?

1) |y-1| =1
2) Angle at Vertex (x,y) = 90 degrees

Source : MGMAT Test

Solution given : (A)

The explanation given in the solution is that :

From Statement (1) either y=0 or y=2, either way base is 5 and height =1. Hence area can be computed

Statement (2) is not enough


I did not understand this explanation. Please help !! Thanks in advance.


Below is almost identical question:

Vertices of a triangle have coordinates (-2, 2), (3, 2), (x, y). What is the area of the triangle?

(1) |y - 2| = 1
(2) angle at the vertex \((x, y)\) equals 90 degrees

Given two points A(-2,2) and B(3,2). Question: Area ABC=?, where C(x,y).

(1) |y-2|=1 --> \(y=3\) or \(y=1\) --> vertex C could be anywhere on the blue line \(y=3\) or anywhere on the red line \(y=1\). But in ANY case the are of ABC will be the same --> \(area=\frac{1}{2}*base*height\) so \(base=AB=5\) and the height would be 1 for any point C (see two possible locations of C: C1 and C2, the heights of ABC1 and ABC2 are the same and equal to 1) --> \(area=\frac{1}{2}*base*height=\frac{5}{2}\). Sufficient.

(2) angle at the vertex C(x,y) equals to 90 degrees --> ABC is a right triangle with hypotenuse AB --> consider AB to be diameter of a circle and in this case C could be anywhere on the circle and it will be right angle (if the diameter of the circle is also the inscribed triangle’s side, then that triangle is a right triangle), thus height of ABC will be different for different location of point C, resulting the different areas (see two possible locations of of C: C3 and C4, heights of ABC3 and ABC4 are different). Not sufficient.

Answer: A.

Hope it heps.



Hey bunuel,
brilliant explanation.

But, i have a silly doubt in this problem. arent we assuming that the base is fixed at (-2, 2), (3, 2). why cant the base be on the unknown point.

from 1st statement we get the value of y as 3 or 1.
why cant the base be on (x,1) and (3,2) or (x,3) and (3,2)?


We can consider any side of a triangle to be the base.
Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 10161
Own Kudos [?]: 16593 [0]
Given Kudos: 4
GMAT 1: 760 Q51 V42
GPA: 3.82
Send PM
Re: Vertices of a traingle are at (-2,1) , (3,1) & (x,y) on a [#permalink]
Expert Reply
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

Vertices of a traingle are at (-2,1) , (3,1) & (x,y) on a coordinate plane. What is the area of the triangle ?

(1) |y-1| =1
(2) Angle at Vertex (x,y) = 90 degrees

If we modify the question, we only need to know the value of y, as the height is only affected by the value of y.
From condition 1, |y-1|=1, y-1=-1,1, or y=0,2
Both makes the height 1, so this is sufficient and the answer is (A).

Once we modify the original condition and the question according to the variable approach method 1, we can solve approximately 30% of DS questions.
User avatar
Non-Human User
Joined: 09 Sep 2013
Posts: 32639
Own Kudos [?]: 821 [0]
Given Kudos: 0
Send PM
Re: Vertices of a traingle are at (-2,1) , (3,1) & (x,y) on a [#permalink]
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.
GMAT Club Bot
Re: Vertices of a traingle are at (-2,1) , (3,1) & (x,y) on a [#permalink]
Moderator:
Math Expert
92893 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne