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Points L, M, and, N have xy-coordinates (2,0), (8,12), and

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Joined: 16 Feb 2012
Posts: 172
Concentration: Finance, Economics
Points L, M, and, N have xy-coordinates (2,0), (8,12), and  [#permalink]

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14 May 2012, 05:12
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Question Stats:

79% (02:11) correct 21% (02:27) wrong based on 214 sessions

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Points L, M, and, N have xy-coordinates (2,0), (8,12), and (14,0), respectively. Points P, Q, and R have xy-coordinates (6,0), (8,4), and (10,0), respectively. What fraction of the area of the triangle LMN is the area of the triangle PQR?

A. $$\frac{1}{9}$$
B. $$\frac{1}{8}$$
C. $$\frac{1}{6}$$
D. $$\frac{1}{5}$$
E. $$\frac{1}{3}$$

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Joined: 02 Sep 2009
Posts: 55228
Re: Points L, M, and, N have xy-coordinates (2,0), (8,12), and  [#permalink]

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14 May 2012, 05:35
Stiv wrote:
Points L, M, and, N have xy-coordinates (2,0), (8,12), and (14,0), respectively. Points P, Q, and R have xy-coordinates (6,0), (8,4), and (10,0), respectively. What fraction of the area of the triangle LMN is the area of the triangle PQR?

A. $$\frac{1}{9}$$
B. $$\frac{1}{8}$$
C. $$\frac{1}{6}$$
D. $$\frac{1}{5}$$
E. $$\frac{1}{3}$$

Look at the diagram below:
Attachment:

Triangles.png [ 13.17 KiB | Viewed 4122 times ]

The area of triangle LMN (red) is 1/2*base*height=1/2*12*12=72;
The area of triangle PQR (blue) is 1/2*base*height=1/2*4*4=8;

The area of PQR is 8/72=1/9 of the area of triangle LMN.

Else you can notice that triangles LMN and PQR are similar. Now, in two similar triangles, the ratio of their areas is the square of the ratio of their sides, therefore since the ratio of the sides is 4/12=1/3 then the ratio of the areas is (1/3)^2=1/9.

Hope it's clear.
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Joined: 11 Sep 2013
Posts: 142
Concentration: Finance, Finance
Re: Points L, M, and, N have xy-coordinates (2,0), (8,12), and  [#permalink]

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25 Apr 2014, 08:27
Bunuel wrote:
Stiv wrote:
Points L, M, and, N have xy-coordinates (2,0), (8,12), and (14,0), respectively. Points P, Q, and R have xy-coordinates (6,0), (8,4), and (10,0), respectively. What fraction of the area of the triangle LMN is the area of the triangle PQR?

A. $$\frac{1}{9}$$
B. $$\frac{1}{8}$$
C. $$\frac{1}{6}$$
D. $$\frac{1}{5}$$
E. $$\frac{1}{3}$$

Look at the diagram below:
Attachment:
Triangles.png

The area of triangle LMN (red) is 1/2*base*height=1/2*12*12=72;
The area of triangle PQR (blue) is 1/2*base*height=1/2*4*4=8;

The area of PQR is 8/72=1/9 of the area of triangle LMN.

Else you can notice that triangles LMN and PQR are similar. Now, in two similar triangles, the ratio of their areas is the square of the ratio of their sides, therefore since the ratio of the sides is 4/12=1/3 then the ratio of the areas is (1/3)^2=1/9.

Hope it's clear.

Hi,
I think I won't try immediately to draw diagram in real exam. So it would be very helpful if you give formula to find area from the points if there is any. Please help me to solve the problem without drawing anything.
Manhattan Prep Instructor
Joined: 22 Mar 2011
Posts: 1450
Re: Points L, M, and, N have xy-coordinates (2,0), (8,12), and  [#permalink]

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25 Apr 2014, 19:42
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If you didn't want to draw, you could notice that both triangles have bases that run along the x-axis. The first triangle has a base that runs from (2,0) to (14,0) and a vertex at (8,12), so that's a base of 12 and a height of 12. The second triangle has a base that runs from (6,0) to (10,0) and a vertex at (8,4), so that's a base of 4 and a height of 4. The second triangle is 1/3 as big in both directions, so it will have 1/9 the area of the first one. (1/3 * 1/3)

Having said all that, most people would probably do best to draw a picture. It doesn't have to be pretty and it should only take a few seconds to make. If it ensures that you visualize the problem correctly, then it's worth it. The step you can skip is actually calculating the areas. You only need to know PQR's area relative to LMN; you don't have to know the actual values.
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Joined: 11 Sep 2013
Posts: 142
Concentration: Finance, Finance
Re: Points L, M, and, N have xy-coordinates (2,0), (8,12), and  [#permalink]

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25 Apr 2014, 20:11
DmitryFarber wrote:
If you didn't want to draw, you could notice that both triangles have bases that run along the x-axis. The first triangle has a base that runs from (2,0) to (14,0) and a vertex at (8,12), so that's a base of 12 and a height of 12. The second triangle has a base that runs from (6,0) to (10,0) and a vertex at (8,4), so that's a base of 4 and a height of 4. The second triangle is 1/3 as big in both directions, so it will have 1/9 the area of the first one. (1/3 * 1/3)

Having said all that, most people would probably do best to draw a picture. It doesn't have to be pretty and it should only take a few seconds to make. If it ensures that you visualize the problem correctly, then it's worth it. The step you can skip is actually calculating the areas. You only need to know PQR's area relative to LMN; you don't have to know the actual values.

Thank you very much. The explanation is helpful.
Director
Affiliations: GMATQuantum
Joined: 19 Apr 2009
Posts: 611
Re: Points L, M, and, N have xy-coordinates (2,0), (8,12), and  [#permalink]

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27 Apr 2014, 12:52
This is a problem from GMATPrep that does not include the first two sentences posted by the original poster, and instead has an image in the coordinate plane. Please see the attached image and use that to solve this problem as opposed to modifying the original problem statement.

Cheers,
Dabral
Attachments

Test1-Q05-PS01.png [ 121.54 KiB | Viewed 2780 times ]

Manager
Joined: 28 Apr 2014
Posts: 206
Re: Points L, M, and, N have xy-coordinates (2,0), (8,12), and  [#permalink]

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28 Apr 2014, 03:42
Raihanuddin wrote:
Bunuel wrote:
Stiv wrote:
Points L, M, and, N have xy-coordinates (2,0), (8,12), and (14,0), respectively. Points P, Q, and R have xy-coordinates (6,0), (8,4), and (10,0), respectively. What fraction of the area of the triangle LMN is the area of the triangle PQR?

A. $$\frac{1}{9}$$
B. $$\frac{1}{8}$$
C. $$\frac{1}{6}$$
D. $$\frac{1}{5}$$
E. $$\frac{1}{3}$$

Look at the diagram below:
Attachment:
Triangles.png

The area of triangle LMN (red) is 1/2*base*height=1/2*12*12=72;
The area of triangle PQR (blue) is 1/2*base*height=1/2*4*4=8;

The area of PQR is 8/72=1/9 of the area of triangle LMN.

Else you can notice that triangles LMN and PQR are similar. Now, in two similar triangles, the ratio of their areas is the square of the ratio of their sides, therefore since the ratio of the sides is 4/12=1/3 then the ratio of the areas is (1/3)^2=1/9.

Hope it's clear.

Hi,
I think I won't try immediately to draw diagram in real exam. So it would be very helpful if you give formula to find area from the points if there is any. Please help me to solve the problem without drawing anything.

I believe formulae is there but it will the solution time-consuming. Definitely not advisable for a strictly timed exam like GMAT
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Joined: 09 Sep 2013
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Re: Points L, M, and, N have xy-coordinates (2,0), (8,12), and  [#permalink]

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29 Nov 2018, 23:22
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Re: Points L, M, and, N have xy-coordinates (2,0), (8,12), and   [#permalink] 29 Nov 2018, 23:22
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