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# In the equation above, k is a constant. If y = 17 when x = 2, what is

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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
Same explanation as Carcass's
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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]

Explanation is same as provided by Carcass above.
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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
2
Kudos
1) Put y =17 and x=2 and solve for K
2) Knowing k=7 from above and x=4 solve for Y ------> Y=31

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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
1 st step : solve given eqn for K by putting values of x and y. u get k=7
snd step : now put banck value of k=7 and x=4 in given eqn and solve for y.
you get y=31

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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
y = kx + 3
17 = k(2) + 3 --> 14 = 2k --> k=7

y = (7)(4) + 3 --> y = 31

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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

y = kx + 3

In the equation above, k is a constant. If y = 17 when x = 2, what is the value of y when x = 4 ?

(A) 34
(B) 31
(C) 14
(D) 11
(E) 7

Practice Questions
Question: 54
Page: 159
Difficulty: 600

GMAT Club is introducing a new project: The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

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given
y=kx+3

y=17 ; x=2

k = 4.

y=? if x = 7

y=31
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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

y = kx + 3

In the equation above, k is a constant. If y = 17 when x = 2, what is the value of y when x = 4 ?

(A) 34
(B) 31
(C) 14
(D) 11
(E) 7

We are given the equation y = kx + 3, where k is a constant.

We are also given that y = 17 when x = 2, so we can plug these values into the equation to first determine a value for k.
y = kx + 3

17 = 2k + 3

14 = 2k

k = 7

We now can determine the value of y when x = 4:

y = kx + 3

y = (7)(4) + 3

y = 28 + 3

y = 31

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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

y = kx + 3

In the equation above, k is a constant. If y = 17 when x = 2, what is the value of y when x = 4 ?

(A) 34
(B) 31
(C) 14
(D) 11
(E) 7

Given: y = kx + 3
Putting values of y and x.

17 = 2k+3; 2k = 14; k = 7.

Once k is known, I can calculate y for any value of x.

y = kx + 3
= {(7) * 4} +3
= 31

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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
The approach is right as seen above.
But I doubt that this question is a 600 difficulty question.
Maybe sub-600 more obviously.
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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
y = kx + 3

In the equation above, k is a constant. If y = 17 when x = 2, what is the value of y when x = 4 ?

(A) 34
(B) 31
(C) 14
(D) 11
(E) 7

May as well to use such approach:
If y = 17 when x = 2 -> 17 = 2k+3
When x = 4, y = 4k+3 = 2*(2k+3)-3=2*17-3=31
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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
My approach inspired by a video I saw on GMATPrepNow was pretty quick.
I saw the y intercept in the equation "y = kx + 3" = 3 which implies coordinate (0,3)
Then the question gave away another coordinate (2,17) which shows that there was a 14 point rise in y with a 2 point run in x
Hence, another 2 point run in x makes x=4 and y=17+14=31
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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
4
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y = kx + 3

In the equation above, k is a constant. If y = 17 when x = 2, what is the value of y when x = 4 ?

17=2K+3
K=14/2=7

y=7*4+3=31
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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
1
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Bunuel wrote:
y = kx + 3

In the equation above, k is a constant. If y = 17 when x = 2, what is the value of y when x = 4 ?

(A) 34
(B) 31
(C) 14
(D) 11
(E) 7

$$y = kx + 3$$

Substitute $$y = 17$$ & $$x = 2$$ in the above equation

Or, $$17 = k*2 + 3$$

Or, $$2k = 14$$

Or, $$k = 7$$

Quote:
what is the value of y when x = 4 ?

Substitute x = 4 in the equation $$y = kx + 3$$

Or, $$y = 7*4 + 3$$

So, $$y = 31$$, Answer must be (B)
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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
$$y=kx+3$$
$$17=2k+3$$
$$k=7$$
now
$$y=4*7+3$$
$$y=31$$
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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

y = kx + 3

In the equation above, k is a constant. If y = 17 when x = 2, what is the value of y when x = 4 ?

(A) 34
(B) 31
(C) 14
(D) 11
(E) 7

Practice Questions
Question: 54
Page: 159
Difficulty: 600

GMAT Club is introducing a new project: The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

Each week we'll be posting several questions from The Official Guide for GMAT® Review, 13th Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.

We'll be glad if you participate in development of this project:
2. Please vote for the best solutions by pressing Kudos button;
3. Please vote for the questions themselves by pressing Kudos button;
4. Please share your views on difficulty level of the questions, so that we have most precise evaluation.

Thank you!

y=kx+3
17 = 2k +3
k= 7

y = 4*7+3=28+3=31

IMO B

Posted from my mobile device
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Re: In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
Hey guys!
I must have not seen here any explanation from the equity.

Look closer, if 2k and 4k are similar with the coefficient 2, i.e. 2*2k, it means that all equation might be similar multiplied by 2. So we understand that y must be doubled and 3 points less (because there is a sum on the right): 17*2-3 = 31. Easier, quicker and logical.

What do you think?
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In the equation above, k is a constant. If y = 17 when x = 2, what is [#permalink]
y=kx+3
then 17=2k+3
17-3= 2k
14=2k both divided by 2 then k=7 therefore
when x=4
y=7*4+3   /c k is constant