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# In the rectangular coordinate system, what is the area of

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Intern
Joined: 17 Dec 2007
Posts: 8
In the rectangular coordinate system, what is the area of  [#permalink]

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Updated on: 07 Nov 2017, 10:58
2
11
00:00

Difficulty:

35% (medium)

Question Stats:

76% (02:24) correct 24% (02:25) wrong based on 349 sessions

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In the rectangular coordinate system, what is the area of triangle PQR with points

Q=(0,3)
R=(7,4)
P(4,0)

A. 12.5
B. 14
C. 10
D. 16
E. 25

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/in-the-recta ... 80659.html

Originally posted by mbsnyc on 19 Dec 2007, 12:00.
Last edited by Bunuel on 07 Nov 2017, 10:58, edited 2 times in total.
Renamed the topic, edited the question, added the OA and moved to PS forum.
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Location: New York City
Re: In the rectangular coordinate system, what is the area of  [#permalink]

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19 Dec 2007, 12:38
mbsnyc wrote:
In the rectangular coordinate system, what is the area of triangle PQR with points

Q=(0,3)
R=(7,4)
P(4,0)

a. 12.5
b. 14
c. 10
d. 16
e. 25

A

plot the points
make a square
subtract all the unnecessary triangles around the plotted triangle.

anyone know a faster way to do this?
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Re: In the rectangular coordinate system, what is the area of  [#permalink]

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19 Dec 2007, 12:41
bmwhype2 wrote:
mbsnyc wrote:
In the rectangular coordinate system, what is the area of triangle PQR with points

Q=(0,3)
R=(7,4)
P(4,0)

a. 12.5
b. 14
c. 10
d. 16
e. 25

A

plot the points
make a square
subtract all the unnecessary triangles around the plotted triangle.

anyone know a faster way to do this?

use distance formula for each of the sides.

sides are 5 5 7
an isos rt triangle.
bh/2 = 5*5 / 2 = 12.5
Intern
Joined: 17 Dec 2007
Posts: 8
Re: In the rectangular coordinate system, what is the area of  [#permalink]

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19 Dec 2007, 12:45
How did you know it was a right triangle and not just isc?
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Re: In the rectangular coordinate system, what is the area of  [#permalink]

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19 Dec 2007, 12:45
1
bmwhype2 wrote:
plot the points
subtract all the unnecessary triangles around the plotted triangle.

The same way
Attachments

t57324.gif [ 2.49 KiB | Viewed 4882 times ]

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Re: In the rectangular coordinate system, what is the area of  [#permalink]

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19 Dec 2007, 12:53
mbsnyc wrote:
How did you know it was a right triangle and not just isc?

you're right. its simply an isosceles triangle. we can infer the height is 7 but im not sure how to get the base.
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Joined: 29 Mar 2007
Posts: 2447
Re: In the rectangular coordinate system, what is the area of  [#permalink]

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19 Dec 2007, 14:00
mbsnyc wrote:
In the rectangular coordinate system, what is the area of triangle PQR with points

Q=(0,3)
R=(7,4)
P(4,0)

a. 12.5
b. 14
c. 10
d. 16
e. 25

I get A.

Using the distance formula I get sides 5,5, 7

5*5/2=12.5
Manager
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Posts: 215
Re: In the rectangular coordinate system, what is the area of  [#permalink]

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05 May 2008, 18:57
2
2
The area of a triangle with co-ordinates (x1,y1), (x2,y2), (x3,y3) is

1/2|x1(y2-y3)+x2(y3-y1)+x3(y1-y2)|
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Re: In the rectangular coordinate system, what is the area of  [#permalink]

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14 Feb 2014, 11:03
can we do this by distance formula..

square root (x2-x1)^2+(y2-y1)^2

I did that by this formula.. M geting 5, 5 and square root 50 respectively of three sides... so 5*5/2=12.5 Ans A.

is it rite? whats another aproach?
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Re: In the rectangular coordinate system, what is the area of  [#permalink]

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15 Feb 2014, 01:05
sanjoo wrote:
can we do this by distance formula..

square root (x2-x1)^2+(y2-y1)^2

I did that by this formula.. M geting 5, 5 and square root 50 respectively of three sides... so 5*5/2=12.5 Ans A.

is it rite? whats another aproach?

Yes you can do it with this formula... simplest and fastest approach.
There are other approaches mentioned in the posts but those involve more steps. Like plotting a trapezium finding its area and then subtracting two 3-4-5 rt angled triangles to get the desired area.
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Re: In the rectangular coordinate system, what is the area of  [#permalink]

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16 Feb 2014, 10:15
http://www.mathopenref.com/coordtrianglearea.html
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Re: In the rectangular coordinate system, what is the area of  [#permalink]

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09 Nov 2014, 22:50
1
1
To figure out if it's a right triangle we should figure out if two of the sides are vertical to each other.

side 1 coordinates are 0,3 and 4,0 => slope = -3/4
side 2 coordinates are 4,0 and 7,4 => slope = 4/3

slope side1 / slope side2 = (-3/4)/(4/3) = -1
sides are perpendicular to each other and the triangle is right.

Now you can calculate
side1 = 5
side2 = 5
area = (side1 x side2) / 2 = 12.5
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Re: In the rectangular coordinate system, what is the area of  [#permalink]

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10 Nov 2014, 01:33
2
1
we should count all three sides of PQR, so we get

5,5,5*sqrt2, meaning it is right triangle with 45, 45, 90 degree angles

so we only need to 5*5/2=12.5

A
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Re: In the rectangular coordinate system, what is the area of  [#permalink]

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29 Dec 2015, 13:48
Adding to the diagram by walker, if once calculates the area of the triangle that has QR as the hypotenuse, it comes to be a non-integer, which subtracted from a whole integer (28) would give a non integer.

The only non integer options is A
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Re: In the rectangular coordinate system, what is the area of  [#permalink]

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07 Nov 2017, 10:59
mbsnyc wrote:
In the rectangular coordinate system, what is the area of triangle PQR with points

Q=(0,3)
R=(7,4)
P(4,0)

A. 12.5
B. 14
C. 10
D. 16
E. 25

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/in-the-recta ... 80659.html
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Re: In the rectangular coordinate system, what is the area of &nbs [#permalink] 07 Nov 2017, 10:59
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