In the equation above, k is a constant.

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boomgoesthegmat: Senior | Next Rank: 100 Posts; Posts: 93; Joined: Mon Apr 25, 2016 2:22 pmFollowed by: 1 member; Thanked: 1 times

by boomgoesthegmat » Wed May 04, 2016 4:30 am

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

OA: B

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Source: Beat The GMAT — Problem Solving | Wed May 04, 2016 4:30 am

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Wed May 04, 2016 5:54 am

boomgoesthegmat 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

OA: B

Let's find the value of k
We're told that y = 17 when x = 2 is one solution to the equation y = kx + 3
This means that 17 = k(2) + 3
Simplify: 17 = 2k + 3
So, 14 = 2k
We get: k = 7

So, the equation is y = 7x + 3
When x = 4, we get y = 7(4) + 3
So, y = 28 + 3 = 31

Answer: B

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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by [email protected] » Sat Apr 07, 2018 2:02 pm

Hi All,

For most Test Takers, working through the basic Arithmetic would arguably be the fastest and easiest approach (as Brent has shown). If you ever get 'stuck' on a question though, it's important to remember that GMAT questions are almost always based around patterns.

With this question, we're told that Y=17 when X=2. With the given equation (Y = KX + 3), you can see that Y is '3 more' than a multiple of 2. We're asked for the value of Y that occurs when X=4, so Y will certainly get bigger.... So which answer is 3 more than a multiple of 4 and is bigger than 17? There's only one...

Final Answer: B

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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Jeff@TargetTestPrep: GMAT Instructor; Posts: 1462; Joined: Thu Apr 09, 2015 9:34 amFollowed by: 22 members; Location: New York, NY; Thanked: 39 times

by Jeff@TargetTestPrep » Tue Apr 10, 2018 10:30 am

boomgoesthegmat 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

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 the constant k.

y = kx + 3

17 = 2k + 3

14 = 2k

k = 7

We now know the constant value of k and so we can determine the value of y when x = 4:

y = kx + 3

y = (7)(4) + 3

y = 28 + 3

y = 31

Answer: B

Jeffrey Miller
Head of GMAT Instruction
[email protected]

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