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If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value

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If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value [#permalink]

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New post 08 Apr 2013, 04:25
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If \(w=\frac{1+x\frac{y}{z^2}}{x+y}\), \(x=\frac{z}{2}\), and \(y=3\frac{z}{4}\),what is the value of w in terms of z?

A. 11z/10
B. 2z/5
C. 3z/10
D. 11z/10
E. 2z/5

I tried to solve the problem several times, but still didn't get the OA.
[Reveal] Spoiler: OA

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Last edited by Bunuel on 08 Apr 2013, 05:50, edited 1 time in total.
Renamed the topic and edited the question.
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Re: If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value [#permalink]

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New post 08 Apr 2013, 05:57
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sandra1122 wrote:
If \(w=\frac{1+x\frac{y}{z^2}}{x+y}\), \(x=\frac{z}{2}\), and \(y=3\frac{z}{4}\),what is the value of w in terms of z?

A. 11z/10
B. 2z/5
C. 3z/10
D. 11z/10
E. 2z/5

I tried to solve the problem several times, but still didn't get the OA.


Notice that options A and D are the same, as well as options B and E, so there are typos in answer choices.

In order A to be the correct answer it should read 11/(10z).

Say z=4, then \(x=\frac{z}{2}=2\), and \(y=3\frac{z}{4}=3\).

So, in this case we'd have that x=2, y=3 and z=4. Plug these values in the fraction to get w=11/40. Now, plug z=4 into the answer choices to see which one yields 11/40. Only A fits (assuming that there IS a typo and A actually must be 11/(10z)).

Hope it helps.
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Re: If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value [#permalink]

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New post 08 Apr 2013, 06:12
Numerator : \(w=1+\frac{z}{2}*\frac{3}{4}z/z^2 =\)
\(1+\frac{z}{2}*\frac{3}{4}z*\frac{1}{z^2}=1+\frac{3}{8}=\frac{11}{8}\)
Denominator: \(\frac{z}{2}+\frac{3}{4}z=\frac{2z+3z}{4}=\frac{5}{4}z\)
All together: \(\frac{11}{8}/\frac{5z}{4}=\frac{11}{8}*\frac{4}{5z}=\frac{11}{10z}\)

Edited: Thanks Bunuel !
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Last edited by Zarrolou on 08 Apr 2013, 06:22, edited 1 time in total.
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Re: If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value [#permalink]

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New post 08 Apr 2013, 06:14
Zarrolou wrote:
Numerator : \(w=1+\frac{z}{2}*\frac{3}{4}z/z^2 =\)
\(1+\frac{z}{2}*\frac{3}{4}z*\frac{1}{z^2}=1+\frac{3}{8}=\frac{11}{8}\)
Denominator: \(\frac{z}{2}+\frac{3}{4}z=\frac{2z+3z}{4}=\frac{5}{4}z\)
All together: \(\frac{11}{8}/\frac{5z}{4}=\frac{11}{8}*\frac{4}{5}z=\frac{11}{10}z\)


(11/8)/(5z/4)=11/(10z) not 11z/10.
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Re: If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value [#permalink]

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New post 08 Apr 2013, 06:20
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Bunuel wrote:
Zarrolou wrote:
Numerator : \(w=1+\frac{z}{2}*\frac{3}{4}z/z^2 =\)
\(1+\frac{z}{2}*\frac{3}{4}z*\frac{1}{z^2}=1+\frac{3}{8}=\frac{11}{8}\)
Denominator: \(\frac{z}{2}+\frac{3}{4}z=\frac{2z+3z}{4}=\frac{5}{4}z\)
All together: \(\frac{11}{8}/\frac{5z}{4}=\frac{11}{8}*\frac{4}{5}z=\frac{11}{10}z\)


(11/8)/(5z/4)=11/(10z) not 11z/10.


You're right. Typing mistake, I went MAD with all those [fraction][/fraction] Tags!
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Re: If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value [#permalink]

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New post 08 Apr 2013, 18:23
ok, 11/10z would fit the answer. Thanks guys.
But B and E aren't really typos, E is actually 2+z/5.
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If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value [#permalink]

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New post 29 Oct 2015, 16:20
Zarrolou wrote:
Numerator : \(w=1+\frac{z}{2}*\frac{3}{4}z/z^2 =\)
\(1+\frac{z}{2}*\frac{3}{4}z*\frac{1}{z^2}=1+\frac{3}{8}=\frac{11}{8}\)
Denominator: \(\frac{z}{2}+\frac{3}{4}z=\frac{2z+3z}{4}=\frac{5}{4}z\)
All together: \(\frac{11}{8}/\frac{5z}{4}=\frac{11}{8}*\frac{4}{5z}=\frac{11}{10z}\)

Edited: Thanks Bunuel !


Hi Zarrolou,

Probably I'm asking a stupid question now, but I'm really confused.

In the OP it says that:
y=3\(\frac{z}{4}\) but then later you re-write this as \(\frac{3}{4}\)z

Isn't y a mixed number that should be \(\frac{12+z}{4}\)?
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Re: If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value [#permalink]

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New post 30 Oct 2015, 01:34
nicksson wrote:
Zarrolou wrote:
Numerator : \(w=1+\frac{z}{2}*\frac{3}{4}z/z^2 =\)
\(1+\frac{z}{2}*\frac{3}{4}z*\frac{1}{z^2}=1+\frac{3}{8}=\frac{11}{8}\)
Denominator: \(\frac{z}{2}+\frac{3}{4}z=\frac{2z+3z}{4}=\frac{5}{4}z\)
All together: \(\frac{11}{8}/\frac{5z}{4}=\frac{11}{8}*\frac{4}{5z}=\frac{11}{10z}\)

Edited: Thanks Bunuel !


Hi Zarrolou,

Probably I'm asking a stupid question now, but I'm really confused.

In the OP it says that:
y=3\(\frac{z}{4}\) but then later you re-write this as \(\frac{3}{4}\)z

Isn't y a mixed number that should be \(\frac{12+z}{4}\)?


It's not a mixed number, it's 3*z/4 and 3/4*z. So, both are the same (3z)/4.
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Resources:
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Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
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Re: If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value [#permalink]

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New post 30 Oct 2015, 03:34
Bunuel wrote:
nicksson wrote:
Zarrolou wrote:
Numerator : \(w=1+\frac{z}{2}*\frac{3}{4}z/z^2 =\)
\(1+\frac{z}{2}*\frac{3}{4}z*\frac{1}{z^2}=1+\frac{3}{8}=\frac{11}{8}\)
Denominator: \(\frac{z}{2}+\frac{3}{4}z=\frac{2z+3z}{4}=\frac{5}{4}z\)
All together: \(\frac{11}{8}/\frac{5z}{4}=\frac{11}{8}*\frac{4}{5z}=\frac{11}{10z}\)

Edited: Thanks Bunuel !


Hi Zarrolou,

Probably I'm asking a stupid question now, but I'm really confused.

In the OP it says that:
y=3\(\frac{z}{4}\) but then later you re-write this as \(\frac{3}{4}\)z

Isn't y a mixed number that should be \(\frac{12+z}{4}\)?


It's not a mixed number, it's 3*z/4 and 3/4*z. So, both are the same (3z)/4.


Thank you Bunuel for your reply.

How do you know when it's a mixt number and when it is 3/4*z because to me they look the same?
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If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value [#permalink]

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New post 30 Oct 2015, 05:17
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Expert's post
nicksson wrote:
Bunuel wrote:
nicksson wrote:

Hi Zarrolou,

Probably I'm asking a stupid question now, but I'm really confused.

In the OP it says that:
y=3\(\frac{z}{4}\) but then later you re-write this as \(\frac{3}{4}\)z

Isn't y a mixed number that should be \(\frac{12+z}{4}\)?


It's not a mixed number, it's 3*z/4 and 3/4*z. So, both are the same (3z)/4.


Thank you Bunuel for your reply.

How do you know when it's a mixt number and when it is 3/4*z because to me they look the same?


If there is a variable involved it's always a multiplication (other case will be explicitly stated).
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Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


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Re: If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value [#permalink]

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New post 16 Dec 2015, 19:13
please have the question removed or edited.
Re: If w=(1+x*y/z^2)(x+y), x=z/2, and y=3z/4, what is the value   [#permalink] 16 Dec 2015, 19:13
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