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For the system of equations given, what is the value of z?

(1) x = 7. Substitute the value of x in the first equation to find z. Sufficient. (2) t = 5. Substitute the value of t in the third equation to find z. Sufficient.

Re: For the system of equations given, what is the value of z? [#permalink]

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12 Sep 2012, 05:24

2

This post received KUDOS

Bunuel wrote:

x-4=z y-x=8 8-z=t

For the system of equations given, what is the value of z?

(1) x = 7 (2) t = 5

St 1: Sufficient: x=7, substituting in Eq 1, we will get value of Z, 7-4=z=3, ST 2. Sufficient: t=5, substituting in Eq 3, We will get value of Z, 8-Z=5, Z= 3.

Hence Answer D.
_________________

Regards SD ----------------------------- Press Kudos if you like my post. Debrief 610-540-580-710(Long Journey): http://gmatclub.com/forum/from-600-540-580-710-finally-achieved-in-4th-attempt-142456.html

For the system of equations given, what is the value of z?

(1) x = 7. Substitute the value of x in the first equation to find z. Sufficient. (2) t = 5. Substitute the value of t in the third equation to find z. Sufficient.

Answer: D.

Kudos points given to everyone with correct solution. Let me know if I missed someone.
_________________

Re: For the system of equations given, what is the value of z? [#permalink]

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18 Jul 2013, 13:58

I didnt even solve for z, all I used was the fact that "ONE unknown and TWO knowns means you can solve for the unknown".

Hence, we are given x in s(1) and that is sufficent just by looking at the top equation. Then we are given t in s(2) which is enough for the third equation.

The reason this method is superior to any other is that you quickly can move on to the next quant problem on the test, I solved this q in 35 seconds using this method.

If there are any holes in this approach, please speak up and correct me.

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