Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 39744

The only gift certificates that a certain store sold [#permalink]
Show Tags
25 Jun 2012, 02:58
Question Stats:
48% (02:57) correct
52% (01:44) wrong based on 844 sessions
HideShow timer Statistics



Math Expert
Joined: 02 Sep 2009
Posts: 39744

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
25 Jun 2012, 02:59
3
This post received KUDOS
Expert's post
8
This post was BOOKMARKED
SOLUTIONThe only gift certificates that a certain store sold yesterday were worth either $100 each or $10 each. If the store sold a total of 20 gift certificates yesterday, how many gift certificates worth $10 each did the store sell yesterday?Say the number of $100 certificates sold was \(x\), then the number of $10 certificates sold was \(20x\). (1) The gift certificates sold by the store yesterday were worth a total of between $1,650 and $1,800 > \(1,650<100x+10(20x)<1,800\) > \(1,650<90x+200<1,800\) > \(1,450<90x<1,600\) > \(145<9x<160\) > \(16.1<x<17.8\). Since \(x\) is an integer then \(x=17\). Sufficient. (2) Yesterday the store sold more than 15 gift certificates worth $100 each > x>15. Clearly insufficient. Answer: A.
_________________
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



Kellogg MMM ThreadMaster
Joined: 29 Mar 2012
Posts: 324
Location: India
GMAT 1: 640 Q50 V26 GMAT 2: 660 Q50 V28 GMAT 3: 730 Q50 V38

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
25 Jun 2012, 08:57
2
This post received KUDOS
Hi,
Difficulty level: 650
Let's say, Number of gift certificates worth $100 = x Number of gift certificates worth $10 = y and x+y=20
Using (1), \(1650<100x+10y<1800\) or \(165<10x+y<180\) or \(165<20+9x<180\) (given, x+y=20) or \(145<9x<160\) or \(145/9<x<160/9\) or \(16.1< x < 17.7\) Thus, x = 17. Sufficient.
Using (2), x > 15. Insufficient.
Answer (A),
Regards,



Intern
Joined: 29 Apr 2012
Posts: 1

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
25 Jun 2012, 18:46
1
This post received KUDOS
(1) The gift certificates sold by the store yesterday were worth a total of between $1 ,650 and $1,800. Suff as only one combination of $100 and $10 GC is possible for total ranging from 16501800 i.e 17 ($100) and 3 ($10) total 1730, all other combinations within this range do not meet total number of GC condition
(2) Yesterday the store sold more than 15 gift certificates worth $100 each
Insuff as more than 15 can mean 16 and 4, 17 and 3, 18 and 2
THerefore A



Manager
Joined: 16 Feb 2012
Posts: 230
Concentration: Finance, Economics

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
26 Jun 2012, 00:30
1
This post received KUDOS
Hi, Difficulty level: 600 Number of gift certificates worth $100 = x Number of gift certificates worth $10 = y and x+y=20 Statement (1) 1650 < x+y < 1800 This gives us only one possible solution... 1730 Since there has to be 20 gift certificates and x=100$ and y=10$, 1730 is the only number that is between 1650 and 1800 that corresponds with 20 gift certificates Every other solution is out of range e.g. 16 x 100$ + 4 x 10$ = 1640$ or 18 x 100$ + 2 x 10$ = 1820$, both out of the range 1650 < x+y < 1800 Statement (2) clearly insufficient since you can have more than one possible solution.
_________________
Kudos if you like the post!
Failing to plan is planning to fail.



Manager
Joined: 02 Jun 2011
Posts: 156

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
26 Jun 2012, 14:52
x+y = 20
st1.) 1650<100x+10y<1800 with ths eqn and x+y = 20 sufficient
st.2) x>15 not sufficient
Answer A.



Math Expert
Joined: 02 Sep 2009
Posts: 39744

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
29 Jun 2012, 04:10
SOLUTIONThe only gift certificates that a certain store sold yesterday were worth either $100 each or $10 each. If the store sold a total of 20 gift certificates yesterday, how many gift certificates worth $10 each did the store sell yesterday?Say the number of $100 certificates sold was \(x\), then the number of $10 certificates sold was \(20x\). (1) The gift certificates sold by the store yesterday were worth a total of between $1,650 and $1,800 > \(1,650<100x+10(20x)<1,800\) > \(1,650<90x+200<1,800\) > \(1,450<90x<1,600\) > \(145<9x<160\) > \(16.1<x<17.8\). Since \(x\) is an integer then \(x=17\). Sufficient. (2) Yesterday the store sold more than 15 gift certificates worth $100 each > x>15. Clearly insufficient. Answer: A.
_________________
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: 10 Sep 2012
Posts: 145

The only gift certificates that a certain store sold [#permalink]
Show Tags
25 Dec 2012, 01:35
Is this a trap question?
That is the intentions of the writer is to make you think that you need 1 and 2 to be able to get the correct answer.
because 2 is obviously not correct and if you weren't able to do 1 properly, you would have to automatically assume that 2 is required.
It seems like it is always advantageous to simply pick the A (or whatever is the harder stem) in these types of questions.



Intern
Joined: 07 Nov 2012
Posts: 7

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
28 Dec 2012, 18:50
1
This post received KUDOS
Yes, this question pretty much wants you to understand that A alone is sufficient, otherwise the fallback answer would be C. St II is obviously not sufficient by itself.



GMAT Club Legend
Joined: 09 Sep 2013
Posts: 16022

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
06 Jul 2014, 03:46
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources



GMAT Club Legend
Joined: 09 Sep 2013
Posts: 16022

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
18 Jul 2015, 22:04
1
This post received KUDOS
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources



Senior Manager
Status: Professional GMAT Tutor
Affiliations: AB, cum laude, Harvard University (Class of '02)
Joined: 10 Jul 2015
Posts: 367
Location: United States (CA)
GMAT 1: 770 Q47 V48 GMAT 2: 730 Q44 V47
GRE 1: 337 Q168 V169
WE: Education (Education)

The only gift certificates that a certain store sold [#permalink]
Show Tags
27 Mar 2016, 19:58
Here is a visual that should help. Nearly every GMAT question can be solved by algebra, plugging in numbers, both, or a combination of both. If you have time, then it's best to try both. This particular method is a hybrid of the two: use algebra to get closer to conceptual understanding, then plug in numbers to test.
Attachments
Screen Shot 20160327 at 7.59.24 PM.png [ 125.32 KiB  Viewed 3777 times ]
_________________
Harvard grad and 770 GMAT scorer, offering highquality private GMAT tutoring, both inperson and via Skype, since 2002.
McElroy Tutoring



GMAT Club Legend
Joined: 09 Sep 2013
Posts: 16022

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
27 Jun 2017, 18:38
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources



Intern
Joined: 18 Aug 2015
Posts: 4
Location: United States
GPA: 3.38

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
28 Jun 2017, 07:04
I approached 1 differently than the posts. Hopefully it helps.
(1) Given that 20 gift cards were sold... I saw 1,650 and tried to rationalize how to break that down. I know that I have to sell 16(100)+4(10) which is short of 1,650.
I progressed to 17(100)+3(10)=1,730 which checks out. 18(100)+2(10)=1820 which is outside the scope.
Therefore, I have only 1 possible answer. Sufficient
(2) Knowing nothing about (1), this is not sufficient by itself. So it cannot be B.
Knowing that (1) is sufficient, we no longer need (2). Not Sufficient




Re: The only gift certificates that a certain store sold
[#permalink]
28 Jun 2017, 07:04







