In the equation above, k is a constant.

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

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