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Co-ordinate Geometry~~

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Co-ordinate Geometry~~

by apoorva.srivastva » Sat Feb 20, 2010 2:07 am
line m and n pass through point (1,2). Is the slope of m greater than the slope of n?

1.) the x-intercept of m is greater than 1 and that of n is less than 1

2.) the y-intercept of m = 4 and that of n = (-2)

OA is D

kindly explains to solve st1 algebraically!!
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by thephoenix » Sat Feb 20, 2010 3:11 am
apoorva.srivastva wrote:line m and n pass through point (1,2). Is the slope of m greater than the slope of n?

1.) the x-intercept of m is greater than 1 and that of n is less than 1

2.) the y-intercept of m = 4 and that of n = (-2)

OA is D

kindly explains to solve st1 algebraically!!

slope is nothing but the angle a lin subtends to Xaxis its the angle from X axis towards Y axis

s1) the two line will be as attched

clearly slope of m> slope of n
s2) the two line will be as attached

clearly slope of m>slope n
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by girish3131 » Sat Feb 20, 2010 5:29 am
@Apoorva


Acc to me, ans is either C or E (will confirm tmrw b/w them)

but am damn sure that Ans can't be D

U to plz check again.

Thanks!
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by harsh.champ » Sat Feb 20, 2010 5:52 am
apoorva.srivastva wrote:line m and n pass through point (1,2). Is the slope of m greater than the slope of n?

1.) the x-intercept of m is greater than 1 and that of n is less than 1

2.) the y-intercept of m = 4 and that of n = (-2)

OA is D

kindly explains to solve st1 algebraically!!
Here is the algebraic explanation:-
Let the line be y=mx +c and y=nx+d
Now putting point(1,2) we get
2=m+c and 2 = n+d
or c=2-m and d=2-n

Statement 1:- x-intercept means y=0
For m we have x= -c/m > 1
For n we have x= -d/n<1
Putting values of c and d from above,we have
(m-2)/m >1 and (n-2)/n < 1
Transposing 1 on the L.H.S.,we get
=>-2/m > 0 and -2/n <0

Since we don't know whether m and n are both +ve or both -ve or have alternate signs we can't tell anything.
Hence,the statement is insufficient.

I hope the above algebraic explanation helps. :)
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by apoorva.srivastva » Sat Feb 20, 2010 7:54 am
girish3131 wrote:@Apoorva


Acc to me, ans is either C or E (will confirm tmrw b/w them)

but am damn sure that Ans can't be D

U to plz check again.

Thanks!
Girish i checked it bro..OA is D :)
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by apoorva.srivastva » Sat Feb 20, 2010 7:57 am
@ harsh...i too feel the st1 is insufficient!!
st2 is sufficient

@ girish....for me the OA should be B!!

someone can u please diagnose the this particular DS ;)
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by harsh.champ » Sat Feb 20, 2010 8:27 am
apoorva.srivastva wrote:@ harsh...i too feel the st1 is insufficient!!
st2 is sufficient

@ girish....for me the OA should be B!!

someone can u please diagnose the this particular DS ;)
line m and n pass through point (1,2). Is the slope of m greater than the slope of n?

1.) the x-intercept of m is greater than 1 and that of n is less than 1

2.) the y-intercept of m = 4 and that of n = (-2)


Ok.I will show it step-by-step
Let the line be y=mx +c and y=nx+d
Now putting point(1,2) we get
2=m+c and 2 = n+d
or c=2-m and d=2-n

From St 2:-
the y-intercept(means x=0) of m = 4,hence we have c = 4
Also,y-intercept of n = (-2) ,hence we have d = -2
But,still we don't know about their slopes m and n(we only have their intercepts c and d)
Hence St 2 is insufficient.

So, the answer cannot be B.
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by harsh.champ » Sat Feb 20, 2010 8:30 am
apoorva.srivastva wrote:
someone can u please diagnose the this particular DS ;)
Now I am posting the soln. approach that I think you might have taken:-

2=m+c and 2 = n+d
or c=2-m and d=2-n
the y-intercept of m = 4,hence we have -c/m = 4(This is when x-intercept is 4)
=>c=-4m
Also,y-intercept of n = (-2) ,hence we have -d/n = -2(This is when x-intercept is -2)
=>d=2n
Putting values of c and d from above,we have
c=2 - m and c=-4m
=>m= -2/3
Also,d=2-n and d=2n
=>n=2/3
Hence,we get the slopes.
I think when you solved the 2nd statement ,the brain did not switch from x-intercept mode to y-intercept mode and hence you solved it by the incorrect method as I have shown.

I hope now you understand the trap in the question.

Hope this illustration will help u apoorva to diagnose this DS. :)
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by kstv » Sat Feb 20, 2010 10:51 am
The lines m and n insertect at (1,2).

(1) m intersect the x axis at > 1 , say (2,0) . It has a - ve slope.

Line n passes the point (1,2) and intersect x axis at , 1 , say 0.5. It hass +ve slope.

Sufficient.

(2) the y intercept of m = 4 and that of n is -2 .

If two points are known the eq. y = mx +c can be solved.

Sufficient
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