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I selected D because stmt2 is also sufficient to say that lines are not perpendicular !!

Because as per stmt2, slope1 and slope2 are NOT reciprocals, it only says that they have opposite signs. So we can safely say that lines are not perpendicular..any comments or counter example?

I selected D because stmt2 is also sufficient to say that lines are not perpendicular !!

Because as per stmt2, slope1 and slope2 are NOT reciprocals, it only says that they have opposite signs. So we can safely say that lines are not perpendicular..any comments or counter example?

If m = 1 ans n = -1, the lines are perpendicular but if m is none other than 1 or -1, then n is also other than 1 or -1. In that case, lines m and n are not perpendicular.

m = -n = 0 is also one option. Are lines m and n perpendicular in that case? _________________

I selected D because stmt2 is also sufficient to say that lines are not perpendicular !!

Because as per stmt2, slope1 and slope2 are NOT reciprocals, it only says that they have opposite signs. So we can safely say that lines are not perpendicular..any comments or counter example?

If m = 1 ans n = -1, the lines are perpendicular but if m is none other than 1 or -1, then n is also other than 1 or -1. In that case, lines m and n are not perpendicular.

m = -n = 0 is also one option. Are lines m and n perpendicular in that case?

No, when m=-n=0 they will be paralel to each other (assuming they are not the same line) and paralel to the x axis. Consider lines y=7 , y=3, y=0, y=-3, y=-7...they all have slope zero and they are paralel to each other and the x axis

Dont seem to find any discussion of this question in the master thread.

If two lines have slopes m and n, respectively, are they perpendicular?

(a) m*n = -1 (b) m = -n

My question is why the OA is not D? Is it correct that based on the second option, we can conclude that the answer is NO?

Am I missing something? Pls help.

For one line to be perpendicular to another, the relationship between their slopes has to be negative reciprocal, so if the slope of one line is m then the line prependicular to it will have the slope -\frac{1}{m}. In other words, the two lines are perpendicular if and only the product of their slopes is -1.

If two lines have slopes m and n, respectively, are they perpendicular?

(1) m*n = -1 --> directly gives an answer YES to the question.

(2) m = -n --> now, if for example m=3=-(-3)=-n then the lines are not perpendicular but if m=1=-(-1)=-n (or m=-1=-1=-n) then as mn would be equal to -1 the lines would be perpendicular. Not sufficient.

Answer: A.

Matt1177 you should have spotted that there was something wrong with your solution as on the GMAT, two data sufficiency statements always provide TRUE information and these statements never contradict each other.

So we can not have answer YES from statement (1) and answer NO from statement (2), as in this case statements would contradict each other.

(2) m = -n --> now, if for example m=3=-(-3)=-n then the lines are not perpendicular but if m=1=-(-1)=-n (or m=-1=-1=-n) then as mn would be equal to -1 the lines would be perpendicular. Not sufficient.

Answer: A.

Matt1177 you should have spotted that there was something wrong with your solution as on the GMAT, two data sufficiency statements always provide TRUE information and these statements never contradict each other.

Yes, I definately remember that the statements in DS shall not be in confllict, this is why I was confused. Totally forgot that 1 and -1 will satisfy the condition. Sorry about that.

Thank you, Bunuel. As always, you are a great help.

If two lines have slopes m and n, respectively, are they perpendicular? 1. m*n = -1 2. m=-n A. Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient B. Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient C.BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient D.EACH statement ALONE is sufficient E. Statements (1) and (2) TOGETHER are NOT sufficient

According to me Answer is D but its wrong. My explanation is Statement (1) by itself is sufficient. Lines and are perpendicular and the product of their slopes is is always equal to -1 . Answer is Yes.

Statement (2) by itself is sufficient. Its states that lines are mirror reflections of each other, but not perpendicular. So asnwer to question is No. Since there is an answer. this is sufficent.