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Re: A line k has a positive slope m and it passes through the point -4, 6 [#permalink]
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Strong like a heck fundamental in math and our book is the best to achieve such skill level https://gre.myprepclub.com/forum/gre-math- ... -2609.html

And a killer persistence

No other secrets
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Re: A line k has a positive slope m and it passes through the point -4, 6 [#permalink]
void wrote:
KarunMendiratta wrote:
KarunMendiratta wrote:
Up for GRE Quant Challenge!!

A line k has a positive slope m and it passes through the point (-4, 6). If the area of the triangle formed by line k, x-axis and y-axis is 54 square units. What is the possible value for \(m\)?

A. 0.25
B. 0.75
C. 1.25
D. 1.75
E. Cannot be determined from the given information


Explanation:

Drop a perpendicular from D(-4, 6) to x-axis (as shown in the figure)
Attachment:
If the area of the triangle formed by line.png


AC = \(x\)
CO = 4
CD = OE = 6
BE = \(y\)

△ACD ~ △AOE
i.e. \(\frac{x}{(x+4)} = \frac{6}{(6+y)} = \sqrt{\frac{Ar. (△ACD)}{ Ar. (△AOE)}} = \sqrt{\frac{3x}{54}}\)

Solve, \(\frac{x}{(x+4)} = \sqrt{\frac{3x}{54}} = \sqrt{\frac{x}{18}}\)

Squaring both sides;
\(\frac{x^2}{(x+4)^2} = \frac{x}{18}\)

\(\frac{x}{(x+4)^2} = \frac{1}{18}\)

\(18x = x^2 + 8x + 16\)
\(x^2 - 10x + 16 = 0\)
\(x^2 - 8x - 2x + 16 = 0\)
\(x(x-8) - 2(x-8) = 0\)
\((x-2)(x-8) = 0\)
\(x = 2\) or \(8\)

Taking \(x=8\), and solve for \(y\);
\(\frac{8}{(8+4)} = \frac{6}{(6+y)}\)
\(48+8y = 72 + 12y\)
\(4y = 36\)
\(y=9\)

Therefore, A is (-12, 0) and B(0, 9)

Apply slope formulae;
\(m = \frac{(9-0)}{(0+12)} = \frac{9}{12} = \frac{3}{4}\)

Hence, option B

[NOTE: if you take \(x=2\), you get \(m=3\) - which is not in the option choices]

thank you for explanation,
but sir how should one come up solution on time or writing exam.....
any suggestion to develop skill to solve problem just like in given question....


Initially start with learning the concepts. Start practicing thereafter, try as many new relevant questions you can to bolster your concepts and approach. Once, you have kind of mastered this, practice against time!

Will surely help you improve your scores significantly.
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Re: A line k has a positive slope m and it passes through the point -4, 6 [#permalink]
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void

as carcass suggested, go through the Math book. You will surely find it to be helpful
https://gre.myprepclub.com/forum/gre-math- ... -2609.html
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Re: A line k has a positive slope m and it passes through the point -4, 6 [#permalink]
1
I did this with different approach. Here we are given area is 54,
>> 0.5*b*h= 54
>> b*h= 108

Factoring 108 gives 2*2*3*3*3

play with this numbers, only 9/12 = 0.75 works.
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A line k has a positive slope m and it passes through the point -4, 6 [#permalink]
kumarneupane4344 wrote:
I did this with different approach. Here we are given area is 54,
>> 0.5*b*h= 54
>> b*h= 108

Factoring 108 gives 2*2*3*3*3

play with this numbers, only 9/12 = 0.75 works.


Dear Sir, why not \(\frac{12}{9} = 1.33\)?
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Re: A line k has a positive slope m and it passes through the point -4, 6 [#permalink]
KarunMendiratta wrote:
kumarneupane4344 wrote:
I did this with different approach. Here we are given area is 54,
>> 0.5*b*h= 54
>> b*h= 108

Factoring 108 gives 2*2*3*3*3

play with this numbers, only 9/12 = 0.75 works.


Dear Sir, why not \(\frac{12}{9} = 1.33\)?


Its because 1.33 is not in our answer choice.
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Re: A line k has a positive slope m and it passes through the point -4, 6 [#permalink]
1
kumarneupane4344 wrote:
KarunMendiratta wrote:
kumarneupane4344 wrote:
I did this with different approach. Here we are given area is 54,
>> 0.5*b*h= 54
>> b*h= 108

Factoring 108 gives 2*2*3*3*3

play with this numbers, only 9/12 = 0.75 works.


Dear Sir, why not \(\frac{12}{9} = 1.33\)?


Its because 1.33 is not in our answer choice.


That is Correct!
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Re: A line k has a positive slope m and it passes through the point -4, 6 [#permalink]
factorize the product of 2*area and the options is the fast way to go!
the option that contains factors in product above is the answer
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Re: A line k has a positive slope m and it passes through the point -4, 6 [#permalink]
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