Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 43373

The only gift certificates that a certain store sold [#permalink]
Show Tags
25 Jun 2012, 01:58
Question Stats:
52% (01:50) correct 48% (01:44) wrong based on 1041 sessions
HideShow timer Statistics



Math Expert
Joined: 02 Sep 2009
Posts: 43373

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
25 Jun 2012, 01:59
2
This post received KUDOS
Expert's post
11
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: Ultimate GMAT Quantitative Megathread  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: 28 Mar 2012
Posts: 320
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, 07:57
3
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, 17:46
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: 215
Concentration: Finance, Economics

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
25 Jun 2012, 23:30
3
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: 149

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
26 Jun 2012, 13:52
x+y = 20
st1.) 1650<100x+10y<1800 with ths eqn and x+y = 20 sufficient
st.2) x>15 not sufficient
Answer A.



Manager
Joined: 10 Sep 2012
Posts: 140

The only gift certificates that a certain store sold [#permalink]
Show Tags
25 Dec 2012, 00:35
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, 17:50
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.



Senior Manager
Status: Professional GMAT Tutor
Affiliations: AB, cum laude, Harvard University (Class of '02)
Joined: 10 Jul 2015
Posts: 479
Location: United States (CA)
Age: 38
GMAT 1: 770 Q47 V48 GMAT 2: 730 Q44 V47 GMAT 3: 750 Q50 V42
GRE 1: 337 Q168 V169
WE: Education (Education)

The only gift certificates that a certain store sold [#permalink]
Show Tags
27 Mar 2016, 18:58
Here is a visual that should help.
Nearly every GMAT question can be solved by algebra, plugging in numbers, both, or a combination of the two. 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 6515 times ]
_________________
Harvard grad and 770 GMAT scorer, offering highquality private GMAT tutoring, both inperson and online via Skype, since 2002.
GMAT Action Plan  McElroy Tutoring
Last edited by mcelroytutoring on 24 Sep 2017, 15:14, edited 2 times in total.



Intern
Joined: 18 Aug 2015
Posts: 17
Location: United States
GPA: 3.38

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
28 Jun 2017, 06:04
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



Intern
Joined: 22 Jan 2017
Posts: 36

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
24 Jul 2017, 15:56
For these diophantine equations, it is actually possible to reduce the question pretty succinctly with algebra. Some people don't need to do that, and it does take a few extra seconds, but if you're interested this is how I did it.
Given:
100(A) + 10(B) = ? A + B = 20
Statement 1:
100(A) + 10(B) = (1650, 1800) > divide the whole equation by 10 to simplify. 10(A) + B = (165, 180) > use the given information to substitute in for A. 10(20B) + B = (165, 180) 200  9B = (165, 180) > subtract 200 and divide by 1. 9B = (20, 35)
How many multiples of 9 are there between 20 and 35? Only one, so you know that B (which is an integer) can only take one value.
Statement 2:
There is more than one option for A and B, and the overall total is not constrained.
ANS: A



Senior Manager
Joined: 29 Jun 2017
Posts: 439
GPA: 4
WE: Engineering (Transportation)

Re: The only gift certificates that a certain store sold [#permalink]
Show Tags
14 Sep 2017, 09:44
Let 10$ =x sales 100$ = 20x 100(20x) + 10x = total sales 200090x = TS 1) 1650<TS<1800 1650<200090x 350<90x 350>90x x<3.something and 200090x<1800 90x<200 90x>200 x> 2.something => x=3 DEFINITE x=3 2) 20x>15 x<5 1,2,3,4 => insufficient A is the answer
_________________
Give Kudos for correct answer and/or if you like the solution.



Intern
Status: Don't watch the clock,Do what it does, Keep Going.
Joined: 10 Jan 2017
Posts: 46

The only gift certificates that a certain store sold [#permalink]
Show Tags
23 Sep 2017, 23:47
i believe this to be one of the "poster boy" questions for the gmat . While solving we should concentrate on the question rather than concentrating on the fact that the time is running out. Here goes the solution. 100x+10y=w and x+y=20
1. 1650<w<1800 x=16 then y=5 so putting this value in the 1st equation. not possible as 1650<w x=17 then y=3 possible x=18 then y=2 not possible as y<1800 2. not sufficient A




The only gift certificates that a certain store sold
[#permalink]
23 Sep 2017, 23:47






