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Comment on Parallelogram Perimeter
Answer to "Question:
Your calculation of perimeter turns to be 4x-4y+18 but it must be 10x-10y+18.
Hope I didn't miss anything.
Be careful. The 3rd set of
Be careful. The 3rd set of brackets (4y - 2x + 2) is not in the same order as the other brackets. I believe you have mixed up your x's and y's
Got your point. Thank you
Hi Brent,
I know this question is not related and apologies for having to post it on this specific video, but could you please explain when the system of equations method is possible to use in a question? What circumstances allow us to apply this approach. I feel I have a hard time knowing when to apply systems of equations for GMAT questions because they do come up a lot.
Thank you!
In most cases, if there's
In most cases, if there's more than one unknown quantity, AND we have more than one piece of information about those unknown quantities, we can typically create a system of equations.
That said, creating a system of equations is not always the best (aka fastest) approach.
The following video talks about how many variables we should/can assign when solving word problems: https://www.gmatprepnow.com/module/gmat-word-problems/video/906
Cheers,
Brent
Hi Brent, can you solve the
Sure, let's solve the two
Sure, let's solve the two linear systems for x and y.
Since opposite sides of a parallelogram are EQUAL length, we can write:
x - y + 6 = 2x - 6y + 13
Rearrange this equation to get: x - 5y = -7
Now let's examine the other pair of equal sides.
We get: 3x - y - 3 = 4y - 2x + 2
Rearrange this equation to get: 5x - 5y = 5
We have the following system:
x - 5y = -7
5x - 5y = 5
Subtract the bottom equation from the top equation to get: -4x = -12
Solve: x = 3
Once we know that x = 3, we can plug it into one of our equations to find the value of y.
So, take x - 5y = -7, and replace x with 3 to get: 3 - 5y = -7
Solve to get: y = 2
So, the solution to the system is x = 3 and y = 2
Cheers,
Brent
Hi Brent,
After getting two equations i solved for X=2, then i decided to substitute in one of the equations to find Y
Equation : X - 5Y = -7, but when i plug X for 2 i get Y=9/5 (Am i going wrong somewhere)
Then when i could find the value of Y i tried another Equation which rightfully game me answer that Y = 1
Equation 2 : 5X - 5Y = 5 (where i plug X=2 to find Y).. In this equation y = 1 it should be same for both equations correct?
Thanks,
Rohan
You have the following system
You have the following system of equations:
X - 5Y = -7
X - Y = 1
When we solve this system for Y, we get Y = 2 and X = 3
In your solution, you got X = 2. Did you mean to say Y = 2?
If not, how did you arrive at X = 2?
Cheers,
Brent
How do we know that -x +5y=7
A linear equation is any
A linear equation is any equation that can be written in the form ax + by = c (or in the form ax - by = c)