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If L and K are lines in xy plane, is the product of the [#permalink]
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31 Jan 2008, 19:24
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If L and K are lines in xy plane, is the product of the slope of L and K equal to 1? (1) Line L passes through the origin and the point (1,2). (2) Line K has xintercept 4 and yintercept 2.
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Re: If l and K are lines in xy plane, is the product of the [#permalink]
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16 Jul 2012, 05:42
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We don't need to calculate anything to answer this question. If L and K are lines in xy plane, is the product of the slope of l and k equal to 1?The product of two lines equal to 1 if these lines are perpendicular to each other. So, the question basically asks whether L and K are perpendicular to each other. Now, if we knew the equations of each line we would be able to answer the question. What do we need to find equation of a line? Since a line is defined by two points, then if we knew any two points of a line then we could get its equatiom (1) Line L passes through the origin and the point (1,2). We have two points of line L: (0, 0) and (1, 2). So, we can get the equation of line L, though we know nothing about line K. Not sufficient. (2) Line K has xintercept 4 and yintercept 2. We have two points of line K: (4, 0) and (0, 2). So, we can get the equation of line K, though we know nothing about line L. Not sufficient. (1)+(2) We know both equation, hence we can answer whether the lines are perpendicular to each other. Sufficient. Answer: C. venmic wrote: Can anyone give a better explanation on this one please
Hovv does K have a slope of 1/2 out of novvhere at all
Please any expert Given two points \((x_1,y_1)\) and \((x_2,y_2)\) on a line, the slope \(m\) of the line is: \(m=\frac{y_2y_1}{x_2x_1}\). Since xintercept of line K is 4, then it passes through point (4, 0) and since yintercept of line K is 2, the it passes through point (0, 2). Hence it's slope is \(m=\frac{20}{04}=\frac{1}{2}\). For more on Coordinate Geometry check: mathcoordinategeometry87652.htmlHope it helps.
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Re: DS  if l and k [#permalink]
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31 Jan 2008, 21:15
blog wrote: If l and K are lines in xy plane, is the product of the slope of l and k equal to 1?
1. Line l passes through the origin and the point (1,2). 2. Line K has xintercept 4 and yintercept 2. C 1: we dont know anything about the other line but we can find the slope of line l = 2 2: again we dont know the other line's slope but k's is 1/2 Together 2*1/2= 1 But you could just realize that 1 and 2 are suff together b/c we know the slopes we are going to get a YES OR A NO NOT BOTH. so u could save some time.



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Re: DS  if l and k [#permalink]
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01 Feb 2008, 10:55
blog wrote: GMATBLACKBELT wrote: blog wrote: If l and K are lines in xy plane, is the product of the slope of l and k equal to 1?
1. Line l passes through the origin and the point (1,2). 2. Line K has xintercept 4 and yintercept 2. C 1: we dont know anything about the other line but we can find the slope of line l = 2 2: again we dont know the other line's slope but k's is 1/2 Together 2*1/2= 1 But you could just realize that 1 and 2 are suff together b/c we know the slopes we are going to get a YES OR A NO NOT BOTH. so u could save some time. how come u get k's = 1/2 in 2 ? (4,0) and (0,2) > (02)/(40) > 2/4 > 1/2 Formula for slope is (y1y2)/(x1x2)



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Re: DS  if l and k [#permalink]
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02 Feb 2008, 14:41
>> Line K has xintercept 4 and yintercept 2. Its not clear if the xintercept is going to be a (4,0). All it said is that xintercept is 4 and yintercept is 2. Even a coordinate of (4,0) equals an xintercept of 4. So the x coordinates can be (4,0) or (4,0) and y coordinates can be (0,2) or (0,2) So there are two possible lines that are perpendicular and the other 2 are not. So in my opinion E. What is the OA ?
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Re: DS  if l and k [#permalink]
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02 Feb 2008, 17:44
my mistake if 1) is true then 2) will have a specific set of coordinates. C is correct... Need to be more cautious.
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Re: DS  if l and k [#permalink]
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02 Feb 2008, 21:51
neelesh wrote: my mistake if 1) is true then 2) will have a specific set of coordinates. C is correct... Need to be more cautious. what do u mean by 2 has to have a specific set of cordinates .. form what i see i agree to your earlier assumption ...when u say line k has 4 as x cordinate and 2 as y cordinate u can very well say that it is a cordinate of the same point (4,2) then u cannot say anything about K's slope as it just passes through one point .. please explain as i still feel it should be E



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Re: If l and K are lines in xy plane, is the product of the [#permalink]
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15 Jul 2012, 23:10
Can anyone give a better explanation on this one please
Hovv does K have a slope of 1/2 out of novvhere at all
Please any expert



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Re: If L and K are lines in xy plane, is the product of the [#permalink]
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20 Oct 2012, 14:46
read 2) carefully  line K has an xintercept of 4 (meaning it hits the x axis at 4 so the point would therefore be 4,0) and yintercept of 2 (meaning it hits the y axis at 2so the point would therefore be 0,2). So we now have (4,0) and (0,2) as our two points for line K and we can plug it into our slope formula of y2  y1/x2  x1 > y2 = 2 y1 = 0 x2  0 y1 = 4 > 20/04 > 2/4 = 1/2.
Hope this helps!



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