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Co-ordinate geometry -2

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Co-ordinate geometry -2

by guerrero » Mon Apr 22, 2013 7:05 am
ABC is a right angle triangle, right angled at B Co ordinates of A, B and C are (X,Z), (X,Y) and (X+3, Y) respectively. Length of line AC is 5 units, x and y are greater than or equal to 0, the vertices of triangle ABC have coordinate values as shown, and the value of AC is as shown. If x = 3, then what could be the slope of line AC?

NOTE : fig. is drawn in 1st quadrant with Z > Y i.e point B is above A.

A. -4/3
B. 2/3
C. 1
D. 4/3
E. 2

OA A
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by Anju@Gurome » Mon Apr 22, 2013 7:43 am
guerrero wrote:ABC is a right angle triangle, right angled at B Co ordinates of A, B and C are (X,Z), (X,Y) and (X+3, Y) respectively. Length of line AC is 5 units, x and y are greater than or equal to 0, the vertices of triangle ABC have coordinate values as shown, and the value of AC is as shown. If x = 3, then what could be the slope of line AC?

NOTE : fig. is drawn in 1st quadrant with Z > Y i.e point B is above A.
Are you sure?
If Z > Y, then as per the problem statement, point A will be above point B because coordinates of A and B are (X, z) and (X, Y).

If that is the case, then refer to the following diagram,
Image
So, AC will have a negative slope.

Only option A works.
[spoiler]
The correct answer is A.[/spoiler]
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by guerrero » Mon Apr 22, 2013 8:06 am
Anju@Gurome wrote:
guerrero wrote:
Are you sure?
If Z > Y, then as per the problem statement, point A will be above point B because coordinates of A and B are (X, z) and (X, Y).

If that is the case, then refer to the following diagram,
Image
So, AC will have a negative slope.

Only option A works.
[spoiler]
The correct answer is A.[/spoiler]
Thanks Anju , this was really simple . The statement kind of confused me .Source is Grockit . I will review it .
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by coolanujdel » Tue Oct 29, 2013 2:32 am
guerrero wrote:
Anju@Gurome wrote:
guerrero wrote:
Are you sure?
If Z > Y, then as per the problem statement, point A will be above point B because coordinates of A and B are (X, z) and (X, Y).

If that is the case, then refer to the following diagram,
Image
So, AC will have a negative slope.

Only option A works.
[spoiler]
The correct answer is A.[/spoiler]
Thanks Anju , this was really simple . The statement kind of confused me .Source is Grockit . I will review it .
How did you know that slope is negative, means how did you get the direction that for Y it will go down?
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by mevicks » Tue Oct 29, 2013 3:38 am
coolanujdel wrote: How did you know that slope is negative, means how did you get the direction that for Y it will go down?
For the GMAT it is very useful to know how a line with a particular slope (positive, negative, zero) actually looks like:

Image

Thus it was easier to select a negative value as the answer.

For more details on this you can read this article : https://www.cliffsnotes.com/math/geometr ... -of-a-line

To calculate the value of the slope:
Referring to the image provided by Anju in the above posts:

We know that X = 3, AC = 5
Thus,
co-ordinate of B = (3, Y)
co-ordinate of C = (6, Y)

The distance BC can be found out from above : BC = 3
Also AB = 4 (Using the property of 3-4-5 right angled triangle)

The new diagram with the co-ordinates updated:
Image

Now, Slope of a line = Rise/Run

Slope of AC = [ y - (y + 4) ] / [ 6 - 3 ] = [spoiler]-4/3 is the slope[/spoiler]
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