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Source: — Data Sufficiency |
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by srcc25anu » Wed Mar 13, 2013 11:37 am
for equation of line Y = mx + c

A states m = 3c. Y= 3cx + c hence not sufficient. there will be mutliple lines that satisfy this condition each with a different Y intercept.

B states X intercept = -1/3. we know nothing about the slope so insufficient.

Together A + B: there will atleast be 2 lines one with +ve slopw and other with -ve slope that cuts x-axis at -1/3 whose slope is 3 times the Y-intercept.

hence insufficient. ANs: E
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by amyhussein » Wed Mar 13, 2013 11:55 am
Together A + B: there will atleast be 2 lines one with +ve slopw and other with -ve slope that cuts x-axis at -1/3 whose slope is 3 times the Y-intercept.
how did you get this information, may you please elaborate more
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by srcc25anu » Wed Mar 13, 2013 12:04 pm
What I am trying to convey is that there will be at least 2 lines that satify the conditions:

Line 1 will pass through (-1/3,0) and (0,-1). For this line Y-intercept is -1.
Line 2 will pass through (-1/3,0) and (0,1). For this line Y-intercept is +1.

hence Not Sufficient. Hope I make myself more clear.
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by Anju@Gurome » Wed Mar 13, 2013 12:09 pm
amyhussein wrote:in the xy plane , what is the y intercept of line L?
A) Slope = 3 times the y intercept
B) X intercept = -1/3
Let us assume that the equation of the line L is y = mx + c
Hence, the slope of L is m and y-intercept is c.

We need to determine c.

Statement 1: m = 3c
As we don't know m, we cannot uniquely determine c.

Not sufficient

Statement 2: x-intercept of L will be the value of x when y = 0 ---> mx + c = 0 ---> x = -c/m
Hence, -c/m = -1/3 ---> m = 3c
Same as statement 1.

Not sufficient

1 & 2 Together: We don't have any new information as both statements are stating the same fact in different manner.

Not sufficient

The correct answer is E.
Anju Agarwal
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by Brent@GMATPrepNow » Wed Mar 13, 2013 12:11 pm
amyhussein wrote:in the xy plane , what is the y intercept of line L?
A) Slope = 3 times the y intercept
B) X intercept = -1/3
Here are two lines that satisfy the conditions in statements 1 and 2.

Image

So, the correct answer is E

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Brent
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