Post your question in the Comment section below, and a GRE expert will answer it as fast as humanly possible.
- Video Course
- Video Course Overview
- General GRE Info and Strategies - 7 videos (free)
- Quantitative Comparison - 7 videos (free)
- Arithmetic - 42 videos
- Powers and Roots - 43 videos
- Algebra and Equation Solving - 78 videos
- Word Problems - 54 videos
- Geometry - 48 videos
- Integer Properties - 34 videos
- Statistics - 28 videos
- Counting - 27 videos
- Probability - 25 videos
- Data Interpretation - 24 videos
- Analytical Writing - 9 videos (free)
- Sentence Equivalence - 39 videos (free)
- Text Completion - 51 videos
- Reading Comprehension - 16 videos
- Study Guide
- Philosophy
- Office Hours
- Extras
- Prices
Comment on Many Variables vs. 2
Suppose if we multiply both
2k-5?2k
2k-5-2k?2k-2k
-5<0
By this way, 0 becomes big
Should not the answer be D? Please correct me if I am wrong anywhere..
Remember that k is a negative
Remember that k is a negative value, and we can't multiply both sides by a negative value (see https://www.greenlighttestprep.com/module/gre-quantitative-comparison/vi...).
HOWEVER, since -k must be a positive value, we can multiply both quantities by -k to get.....
Quantity A: -2k + 5 and Quantity B: -2k
Then add -2k to both sides to get....
Quantity A: 5 and Quantity B: 0
Answer = A
I so appreciate how dedicated
The "last" step, in which Qty A equals [2 - (5/k)], at 1:07, could be a bit confusing.
I refer to this step:
Qty A = 2 - (5/k)
Qty B = 2
I think we can simplify a little further.
Subtract 2 from both quantities.
1. Before
Qty A = 2 - 5/k
Qty B = 2
2. Now subtract 2 from both. Result:
Qty A = -5/k
Qty B = 0
It is given that k<0.
In other words, k is NEGATIVE
Thus, the denominator of the fraction in Qty A is a NEGATIVE number. So too is the numerator (-5).
Hence we can say:
Qty A = (-5/k) = (NEG/NEG) = POSITIVE
Now we have
Qty A = some POSITIVE number
Qty B = 0
Any positive number (Qty A) is greater than 0 (Qty B), so the answer is "A."
Just a thought. :)
Thanks for the kind words!
Thanks for the kind words!
Your proposed solution is perfect and probably easier to follow than mine at the end.
Great work!!
Simplifying 2k/k is obviously
The proviso is at the very
The proviso is at the very top where we say that k < 0
K can also be -5 and 5/-5= -1
Be careful, Kentrell.
Be careful, Kentrell.
If k = -5, then Quantity A evaluates to be 3 (not 2)
Cheers,
Brent
Why can't we eliminate k-1 if
This is covered in the
This is covered in the previous video at https://www.greenlighttestprep.com/module/gre-algebra-and-equation-solvi...
Here's a modified version of the question.
Let's say we want to simplify (2k - 2)/(5k - 5)
We can factor top and bottom to get: 2(k - 1)/5(k - 1)
At this point, we probably want to cancel the (k-1) to get 2/5
HOWEVER, we can only do so if k ≠ 1
Here's why:
If k = 1, then (2k - 2)/(5k - 5) = 0/0, which does NOT equal 2/5
So, if k = 1, we can't say that (2k - 2)/(5k - 5) = 2/5
However, for ANY OTHER value of k, we can say that (2k - 2)/(5k - 5) = 2/5
For example,
- if k = 3, then (2k - 2)/(5k - 5) = (6 - 2)/(15 - 5) = 4/10 = 2/5
- if k = 8, then (2k - 2)/(5k - 5) = (16 - 2)/(40 - 5) = 14/35 = 2/5
- if k = -2, then (2k - 2)/(5k - 5) = (-4 - 2)/(-10 - 5) = -6/-15 = 2/5
etc
Cheers,
Brent
Understood. Thanks
Hello,
But in the case that k=-0.001
The answer will vary.
2-(5/k)
Is there something I am missing so I an getting another answer.
Thank you
If k = -0.001, then 5/k = 5/(
If k = -0.001, then 5/k = 5/(-0.001) = -5000
So, 2 - (5/k) = 2 - (-5000) = 5002
This means Quantity A is still greater than Quantity B.
Does that help?
Cheers,
Brent
Apologies - I realized I
I'm not 100% sure what you're
I'm not 100% sure what you're asking.
In the above discussion, I say that (2k - 2)/(5k - 5) = 2/5 for MOST values of k.
However, if k = 1, then (2k - 2)/(5k - 5) does NOT equal 2/5
My example, (2k - 2)/(5k - 5) = 2/5, it's just that, an example.
Notice that this equation does not match the equation in the original video question above. It's just an example I used to illustrate an important property.
-------------------------
In your question you ask, "If Quantity B were to be 2/5, would the answer be D?
Are you referring to the original question, or my modified question (with Quantity A = (2k - 2)/(5k - 5))?
Hello Brent, I'm unable to
Very odd. I'll get my
Very odd. I'll get my programmer on it.
It works now
Good stuff!
Good stuff!