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# What is the slope of line l? (1) Line l and line m are perpendicular.

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Math Expert
Joined: 02 Sep 2009
Posts: 58464
What is the slope of line l? (1) Line l and line m are perpendicular.  [#permalink]

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29 Aug 2018, 01:27
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Difficulty:

15% (low)

Question Stats:

91% (00:44) correct 9% (00:27) wrong based on 37 sessions

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What is the slope of line l?

(1) Line l and line m are perpendicular.
(2) Line m has y–intercept 6 and passes through the point (–3, 5).

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Director
Joined: 20 Feb 2015
Posts: 756
Concentration: Strategy, General Management
What is the slope of line l? (1) Line l and line m are perpendicular.  [#permalink]

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29 Aug 2018, 01:42
Bunuel wrote:
What is the slope of line l?

(1) Line l and line m are perpendicular.
(2) Line m has y–intercept 6 and passes through the point (–3, 5).

(1) Line l and line m are perpendicular.
the two lines can have any orientation
insufficient.

(2) Line m has y–intercept 6 and passes through the point (–3, 5).
point slope form of the line is given by y =mx+c
substituting the value
5=m(-3) + 6
m=1/3

insufficient

using both

we know that for two perpendicular lines m1*m2=-1
where m1 and m2 are respective slopes

substituting the value we can get the value of m2
sufficient.
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Re: What is the slope of line l? (1) Line l and line m are perpendicular.  [#permalink]

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29 Aug 2018, 02:40
Hi,

It’s a pretty straight-forward question.

Question: What is the slope of line l ?

Rule: If two lines are perpendicular to each other, then the product of their slopes are equal to -1.

Statement I is insufficient:

Line l and line m are perpendicular.

According to the above rule, we know that product of the slopes of lines m and l is equal to -1

But we don’t know the slope of both the lines. So we cant find the slope of line l.

So statement I is insufficient.

Statement II is insufficient:

Line m has y–intercept 6, i.e., (0,6) and passes through the point (–3, 5).

Given two points, we can find the slope of line m. (No need to find the final value as long as we are clear that there is will be only one value).

But question is about slope of line l.

So insufficient.

Together it is sufficient,

We can find the slope of line l, as line “m” and line “l” are perpendicular to each other and slope of “m” is given in statement II.

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GMAT Mentors
Re: What is the slope of line l? (1) Line l and line m are perpendicular.   [#permalink] 29 Aug 2018, 02:40
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