GMATPrep geometry

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GmatKiss: Legendary Member; Posts: 2789; Joined: Tue Jul 26, 2011 12:19 amFollowed by: 43 members; Location: Chennai, India; Thanked: 206 times; GMAT Score:640

by GmatKiss » Sat Oct 29, 2011 7:13 am

In the XY Plane, line K passes through the point (1,1) and line M passes through the point (1, -1). Are lines K and M perpendicular to each other?

(1) Lines k and m intersect at the point (1, -1)
(2) Line k intersects the x-axis at the point (1, 0)

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Source: Beat The GMAT — Data Sufficiency | Sat Oct 29, 2011 7:13 am

rijul007: Legendary Member; Posts: 588; Joined: Sun Oct 16, 2011 9:42 amFollowed by: 9 members; Location: New Delhi, India; Thanked: 130 times; GMAT Score:720

by rijul007 » Sat Oct 29, 2011 8:45 am

[edited]

K passes through the point (1,1) and M passes through the point (1,-1)

Statement 1
Line k and m intersect at (1,-1)

We get the slope of line k , which is parellel to the Y-axis

but we have no clue about the slope of line m
Not sufficient

Statement 2
Line k intersects the x-axis at (1,0)

line k is parellel to y axis .
but this time we have no idea about the slope of line m
Not Sufficient

but combining both the statements also wont tell us aythin about line

Option E

Last edited by rijul007 on Sat Oct 29, 2011 11:10 am, edited 1 time in total.

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studentps2011: Senior | Next Rank: 100 Posts; Posts: 40; Joined: Fri Jul 15, 2011 5:37 am; Thanked: 3 times

by studentps2011 » Sat Oct 29, 2011 9:55 am

Both statements tell us that line k is parallel to y axis and that it meets m at point (1,-1).
But we don't have any further information on line m.
It may be parallel to x axis (slope 0) and thus be perpendicular to line k
OR
have a negative or positive slope and not be perpendicular to line k.

Hence insufficient (E)

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parul9: Master | Next Rank: 500 Posts; Posts: 197; Joined: Thu Sep 15, 2011 10:22 amFollowed by: 2 members; Thanked: 6 times

by parul9 » Sat Oct 29, 2011 10:21 am

Statement 1 says that K is parallel to Y axis, and intersects with M at (1,-1), so these two lines intersect. But it tells nothing about the slope of M. So insufficient.

Statement 2 also says the same thing but does not tell anything about the slope of M. Insufficient.

Combining 1 and 2 also tells nothing about the slope of M.

So, answer should be E.

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