In the xy-plane, line A has slope a and line B has slope b.

Question

In the xy-plane, line A has slope a and line B has slope b. Are the two lines parallel to each other?

1). 4^a=2^b

2). 2^a=3^b 

sorry no OA, can someone explain ? it must be either B or C

haas_mba07 · Answer

Given :
Line A slope = a
Line B slope = b

Q: Is A || B i.e. a = b?

S1: 
4^a = 2^b
2^2a = 2^b 

or 2a = b


Sufficient. (Not ||)

S2: 2^a =3^b

For no power of a & b are these two equal.
Therefore a is not equal to B.
Sufficient.

Not parallel.

Answer: D

haas_mba07 · Answer

Note that the question asks if they are ||... 

The information in S1 and S2 gives us information to say that the two lines are not parallel.

zorro13 · Answer

For me (A).

I: The answer is no. SUFF

II: When a=b=0 then 2^a=3^b....INSUFF.

haas_mba07 · Answer

Interesting point...


For S2: if a = b = 0, then 2^a = 3^b, which is the only possible value. 

So this sufficient.

But shouldn't this be D then...

iced_tea · Answer

this is really interesting. I am picking A here for 2 reasons

a) when a = b = 0, they could be same lines too - in that case are they parallel ??? I am not sure.
b) I have read at couple of places that for DS answers choices do not contradict if both statements are sufficient - in this case they do as 1 says they are not parallel and 2 says they are parallel.

haas_mba07 · Answer

Thats what I've heard... the two answers don't contradict.
Atleast on the GMAT... might not be the case for other questions.

In the xy-plane, line A has slope a and line B has slope b.

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