Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 39626

The Discreet Charm of the DS [#permalink]
Show Tags
02 Feb 2012, 04:15
23
This post received KUDOS
Expert's post
125
This post was BOOKMARKED
I'm posting the next set of medium/hard DS questions. I'll post OA's with detailed explanations after some discussion. Please, post your solutions along with the answers. Good luck!1. Bonnie can paint a stolen car in x hours, and Clyde can paint the same car in y hours. They start working simultaneously and independently at their respective constant rates at 9:45am. If both x and y are odd integers, is x=y?(1) x^2+y^2<12 (2) Bonnie and Clyde complete the painting of the car at 10:30am Solution: thediscreetcharmoftheds12696220.html#p10396332. Is xy<=1/2? (1) x^2+y^2=1 (2) x^2y^2=0 Solution: thediscreetcharmoftheds12696220.html#p10396343. If a, b and c are integers, is abc an even integer?(1) b is halfway between a and c (2) a = b  c Solution: thediscreetcharmoftheds12696240.html#p10396374. How many numbers of 5 consecutive positive integers is divisible by 4?(1) The median of these numbers is odd (2) The average (arithmetic mean) of these numbers is a prime number Solution: thediscreetcharmoftheds12696240.html#p10396455. What is the value of integer x?(1) 2x^2+9<9x (2) x+10=2x+8 Solution: thediscreetcharmoftheds12696240.html#p10396506. If a and b are integers and ab=2, is a=2?(1) b+3 is not a prime number (2) a>b Solution: thediscreetcharmoftheds12696240.html#p10396517. A certain fruit stand sold total of 76 oranges to 19 customers. How many of them bought only one orange?(1) None of the customers bought more than 4 oranges (2) The difference between the number of oranges bought by any two customers is even Solution: thediscreetcharmoftheds12696240.html#p10396558. If x=0.abcd, where a, b, c and d are digits from 0 to 9, inclusive, is x>7/9?(1) a+b>14 (2) ac>6 Solution: thediscreetcharmoftheds12696240.html#p10396629. If x and y are negative numbers, is x<y?(1) 3x + 4 < 2y + 3 (2) 2x  3 < 3y  4 Solution: thediscreetcharmoftheds12696240.html#p103966510. The function f is defined for all positive integers a and b by the following rule: f(a,b)=(a+b)/GCF(a,b), where GCF(a,b) is the greatest common factor of a and b. If f(10,x)=11, what is the value of x?(1) x is a square of an integer (2) The sum of the distinct prime factors of x is a prime number. Solution: thediscreetcharmoftheds12696240.html#p103967111. If x and y are integers, is x a positive integer?(1) x*y is a prime number. (2) x*y is nonnegative integer. Solution: thediscreetcharmoftheds12696240.html#p103967812. If 6a=3b=7c, what is the value of a+b+c?(1) ac=6b (2) 5b=8a+4c Solution: thediscreetcharmoftheds12696240.html#p1039680
_________________
New to the Math Forum? Please read this: All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
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? Extrahard Quant Tests with Brilliant Analytics



Manager
Joined: 26 Jun 2011
Posts: 249
Location: India

Re: The Discreet Charm of the DS [#permalink]
Show Tags
02 Feb 2012, 04:58
2
This post received KUDOS
1.B 2.A 3.B 4.D 5.A 6.E
_________________
The chase begins ...



Intern
Joined: 04 Aug 2011
Posts: 43
Location: United States
Concentration: Technology, Leadership
GPA: 4
WE: Information Technology (Computer Software)

Re: The Discreet Charm of the DS [#permalink]
Show Tags
02 Feb 2012, 06:55
1. B 2. A 3. B 4. D 5. D 6. E 7. D 8. C 9. B 10. C 11. D 12. E



Manager
Joined: 06 Oct 2011
Posts: 165
GMAT Date: 06302012
GPA: 3.7
WE: Accounting (Insurance)

Re: The Discreet Charm of the DS [#permalink]
Show Tags
02 Feb 2012, 07:48
time to get cracking... thanks for posting
_________________
Reward wisdom with kudos



Intern
Joined: 16 Jan 2012
Posts: 29

Re: The Discreet Charm of the DS [#permalink]
Show Tags
02 Feb 2012, 11:55
1b 2a 3b 4a 5b 6e 7d 8b 9e 10a 11d 12a



Intern
Joined: 13 Jul 2011
Posts: 42

Re: The Discreet Charm of the DS [#permalink]
Show Tags
02 Feb 2012, 19:01
Ans: 1B 2A 3A 4E 5D 6E 7C 8A 9C 10A 11D 12D



Math Expert
Joined: 02 Sep 2009
Posts: 39626

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 03:36



Intern
Joined: 04 Aug 2011
Posts: 43
Location: United States
Concentration: Technology, Leadership
GPA: 4
WE: Information Technology (Computer Software)

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 07:51
1. Bonnie can paint a stolen car in x hours, and Clyde can paint the same car in y hours. They start working simultaneously and independently at their respective constant rates at 9:45am. If both x and y are odd integers, is x=y? (1) x^2+y^2<12 (2) Bonnie and Clyde complete the painting of the car at 10:30am
The catch is that they are working independently.
stmt 1  no relation there are can be multiple values of x and y stmt 2  both started at same time, finished at same time with no breaks means they have same working rate proves x = y sufficient
Answer B



Intern
Joined: 04 Aug 2011
Posts: 43
Location: United States
Concentration: Technology, Leadership
GPA: 4
WE: Information Technology (Computer Software)

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 07:56
2. Is xy<=1/2? (1) x^2+y^2=1 (2) x^2y^2=0
My funda  Area of square is largest among all the quadilateral with same perimeter. Stmt 1  Only possible values of x and y are 1/Sqrt(2). So sufficient as xy = 1/2 Stmt 2  Only says x and y are equal. Not sufficient Answer A



Math Expert
Joined: 02 Sep 2009
Posts: 39626

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 07:57
sourabhsoni wrote: 1. Bonnie can paint a stolen car in x hours, and Clyde can paint the same car in y hours. They start working simultaneously and independently at their respective constant rates at 9:45am. If both x and y are odd integers, is x=y? (1) x^2+y^2<12 (2) Bonnie and Clyde complete the painting of the car at 10:30am
The catch is that they are working independently.
stmt 1  no relation there are can be multiple values of x and y stmt 2  both started at same time, finished at same time with no breaks means they have same working rate proves x = y sufficient
Answer B The logic for (2) is not correct, (though I'm not saying that (2) is insufficient). Even if two entities have different rates if they work together they both stop when the job is done.
_________________
New to the Math Forum? Please read this: All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
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? Extrahard Quant Tests with Brilliant Analytics



Math Expert
Joined: 02 Sep 2009
Posts: 39626

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 08:00



Intern
Joined: 04 Aug 2011
Posts: 43
Location: United States
Concentration: Technology, Leadership
GPA: 4
WE: Information Technology (Computer Software)

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 08:01
1
This post received KUDOS
3. If a, b and c are integers, is abc an even integer? (1) b is halfway between a and c (2) a = b  c
Funda for product abc to be even, if any one of them even then product will be even.
Stmt 1  says b = (a+c)/2 means a+c is some even number. E + E also results in even O + O also results in Even and b can be anything even or odd so not sufficient.
Stmt 2  says a = b  c say worst condition b an c are odd . will results in a even. or lets says any one among b or c is even then a off but since one number is even the product will be even so sufficient.
Answer B



Math Expert
Joined: 02 Sep 2009
Posts: 39626

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 08:04



Manager
Joined: 31 Jan 2012
Posts: 74

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 08:43
1)b 2)a 3)b 4)d 5)d 6)e 7)d 8)c 9)e 10)a 11)d 12)a



Intern
Joined: 04 Aug 2011
Posts: 43
Location: United States
Concentration: Technology, Leadership
GPA: 4
WE: Information Technology (Computer Software)

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 08:52
Bunuel wrote: sourabhsoni wrote: 1. Bonnie can paint a stolen car in x hours, and Clyde can paint the same car in y hours. They start working simultaneously and independently at their respective constant rates at 9:45am. If both x and y are odd integers, is x=y? (1) x^2+y^2<12 (2) Bonnie and Clyde complete the painting of the car at 10:30am
The catch is that they are working independently.
stmt 1  no relation there are can be multiple values of x and y stmt 2  both started at same time, finished at same time with no breaks means they have same working rate proves x = y sufficient
Answer B The logic for (2) is not correct, (though I'm not saying that (2) is insufficient). Even if two entities have different rates if they work together they both stop when the job is done.  yes but isn't it correct to say that when they are working independently and starting at same time (as per the question) and ending at same time as per stmt 2 then they must be working at same rate  i.e. X = Y... As stmt 2 doesn't say they are not working together.



Math Expert
Joined: 02 Sep 2009
Posts: 39626

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 08:59
sourabhsoni wrote: yes but isn't it correct to say that when they are working independently and starting at same time (as per the question) and ending at same time as per stmt 2 then they must be working at same rate  i.e. X = Y...
As stmt 2 doesn't say they are not working together. No, that's not correct. Again when: two or more entities (machines, people, ...) are working together they all stop working when the job is done, no matter what their respective rates are. I think that you are thrown away by the phrase "they start working simultaneously and independently", which simply means that they start at the same time and work together (obviously they will also end the work at the same time, when the work is done). Hope it's clear.
_________________
New to the Math Forum? Please read this: All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
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? Extrahard Quant Tests with Brilliant Analytics



Manager
Joined: 31 Jan 2012
Posts: 74

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 09:00
1
This post received KUDOS
1) statement 2 means
rate = 1/x + 1/y = 4/3 (1/[45 mins/ 60 mins]).
The only integer that would work is 1 n 3. Therefore x =/=y. Since X has to be 1 or 3 and Y is whatever X isn't.



Math Expert
Joined: 02 Sep 2009
Posts: 39626

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 09:08



Manager
Joined: 26 Jun 2011
Posts: 249
Location: India

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 14:52
7.A 8.C 9.B 10.C 11.D 12.B
_________________
The chase begins ...



Intern
Joined: 04 Aug 2011
Posts: 43
Location: United States
Concentration: Technology, Leadership
GPA: 4
WE: Information Technology (Computer Software)

Re: The Discreet Charm of the DS [#permalink]
Show Tags
03 Feb 2012, 14:56
1
This post received KUDOS
4. How many numbers of 5 consecutive positive integers is divisible by 4? (1) The median of these numbers is odd (2) The average (arithmetic mean) of these numbers is a prime number
out of 5 consecutive intergers there are only 2 option either there will 1 or 2 numbers which will divide by 4. There will 2 numbers if the first number fo sequence will be divible by 4. So we have to find out if first number is divisible by 4.
Stmt 1  Median is odd means first number is odd ( odd , even , odd, even, odd) So sufficuent to tell that there will only 1 number which be divible by 4. Stmt 2  In case of consecutive numbers median is always equal to average. Numbers are positive so first numbers cannot be 0 to make 2 as median/average. Which means average/mean is odd, Again going by logic in stmt 1 first number should be odd which is also sufficient
Answer D.




Re: The Discreet Charm of the DS
[#permalink]
03 Feb 2012, 14:56



Go to page
1 2 3 4 5 6 7 8 9 10
Next
[ 190 posts ]




