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If x, y, and z are numbers, is z = 18 ?

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If x, y, and z are numbers, is z = 18 ? [#permalink]

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The Official Guide For GMAT® Quantitative Review, 2ND Edition

If x, y, and z are numbers, is z = 18 ?

(1) The average (arithmetic mean) of x, y, and z is 6.
(2) x = -y

Data Sufficiency
Question: 74
Category: Arithmetic Statistics
Page: 158
Difficulty: 600


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Kudos [?]: 70347 [0], given: 9844

Re: If x, y, and z are numbers, is z = 18 ? [#permalink]

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New post 04 Feb 2014, 01:52
Expert's post
SOLUTION

If x, y, and z are numbers, is z = 18 ?

(1) The average (arithmetic mean) of x, y, and z is 6 --> x + y + z = 6*3 = 18. We cannot say whether z = 18. Not sufficient.

(2) x = -y --> x + y = 0. Clearly insufficient.

(1)+(2) x + y + z = 18 --> 0 + z = 18 --> z = 18. Sufficient.

Answer: C.
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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 x, y, and z are numbers, is z = 18 ? [#permalink]

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New post 04 Feb 2014, 04:38
Ans. C

From S1: x+y+z=18.Not sufficient

From S2: x+y=0.Not sufficent to determine z

Combining the two we get z=18 definitely.Both are together sufficient.
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Re: If x, y, and z are numbers, is z = 18 ? [#permalink]

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New post 04 Feb 2014, 05:37
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My answer is also C (explanation is already provided, so not doing honours)
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Kudos [?]: 70347 [0], given: 9844

Re: If x, y, and z are numbers, is z = 18 ? [#permalink]

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New post 08 Feb 2014, 05:38
Expert's post
SOLUTION

If x, y, and z are numbers, is z = 18 ?

(1) The average (arithmetic mean) of x, y, and z is 6 --> x + y + z = 6*3 = 18. We cannot say whether z = 18. Not sufficient.

(2) x = -y --> x + y = 0. Clearly insufficient.

(1)+(2) x + y + z = 18 --> 0 + z = 18 --> z = 18. Sufficient.

Answer: C.
_________________

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Please read this: All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

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?
Extra-hard Quant Tests with Brilliant Analytics

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If x, y, and z are numbers, is z = 18 ? [#permalink]

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New post 30 Sep 2015, 13:10
Bunuel wrote:
SOLUTION

If x, y, and z are numbers, is z = 18 ?

(1) The average (arithmetic mean) of x, y, and z is 6 --> x + y + z = 6*3 = 18. We cannot say whether z = 18. Not sufficient.

(2) x = -y --> x + y = 0. Clearly insufficient.

(1)+(2) x + y + z = 18 --> 0 + z = 18 --> z = 18. Sufficient.

Answer: C.



Dear Bunnel,
Here,Is it possible to guess that number could be in a fraction format too?like \(\frac{1}{5}\)+\(\frac{-1}{5}\)=0 for x+y=0
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Re: If x, y, and z are numbers, is z = 18 ? [#permalink]

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New post 30 Sep 2015, 23:16
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AbdurRakib wrote:
Bunuel wrote:
SOLUTION

If x, y, and z are numbers, is z = 18 ?

(1) The average (arithmetic mean) of x, y, and z is 6 --> x + y + z = 6*3 = 18. We cannot say whether z = 18. Not sufficient.

(2) x = -y --> x + y = 0. Clearly insufficient.

(1)+(2) x + y + z = 18 --> 0 + z = 18 --> z = 18. Sufficient.

Answer: C.



Dear Bunnel,
Here,Is it possible to guess that number could be in a fraction format too?like \(\frac{1}{5}\)+\(\frac{-1}{5}\)=0 for x+y=0


Yes, x and y could be fractions. In fact they could be any real numbers satisfying x + y = 0.
_________________

New to the Math Forum?
Please read this: All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

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 x, y, and z are numbers, is z = 18 ?   [#permalink] 30 Sep 2015, 23:16
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