GRE Prep Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
If 3x + y = − 1 and y − 2x = 4, what is the value of x + 2y?
[#permalink]
02 Mar 2019, 11:27
02 Mar 2019, 11:27
Expert Reply
1
Bookmarks
00:00
Question Stats:
69% (00:51) correct
30% (00:22) wrong based on 68 sessions
Hide Show timer Statistics
If \(3x + y = − 1\) and \(y − 2x = 4\), what is the value of \(x + 2y\)?
A. − 5
B. − 3
C. 0
D. 3
E. 5
A. − 5
B. − 3
C. 0
D. 3
E. 5
Re: If 3x + y = − 1 and y − 2x = 4, what is the value of x + 2y?
[#permalink]
10 Mar 2019, 10:41
10 Mar 2019, 10:41
Expert Reply
We could solve for x and then solve for y and then solve for x + 2y. However, whenever the test asks you to solve for an expression, then there's almost always a neat shortcut you can use to get it.
Here's our two equations:
3x + y = − 1
y − 2x = 4
For clarity, I'll rewrite the top equation slightly:
y + 3x = − 1
y − 2x = 4
And now I'll just add the two equations:
2y + x = 3
And how convenient, that's the answer we were looking for!
Here's our two equations:
3x + y = − 1
y − 2x = 4
For clarity, I'll rewrite the top equation slightly:
y + 3x = − 1
y − 2x = 4
And now I'll just add the two equations:
2y + x = 3
And how convenient, that's the answer we were looking for!
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Given Kudos: 136
Re: If 3x + y = 1 and y 2x = 4, what is the value of x + 2y?
[#permalink]
23 Mar 2022, 11:55
23 Mar 2022, 11:55
1
Carcass wrote:
If \(3x + y = − 1\) and \(y − 2x = 4\), what is the value of \(x + 2y\)?
A. − 5
B. − 3
C. 0
D. 3
E. 5
A. − 5
B. − 3
C. 0
D. 3
E. 5
Important: Notice that the question is not asking us to find the individual values of x and y. On the GRE, this often means we can determine the answer without finding the individual values. That's the case here
Given:
3x + y = − 1
y − 2x = 4
Rearrange the bottom equation as follows:
3x + y = − 1
−2x + y = 4
ADD the two equations to get: x + 2y = 3
Answer: D
