• NEW! FREE Beat The GMAT Quizzes  Hundreds of Questions Highly Detailed Reporting Expert Explanations
• 7 CATs FREE!
If you earn 100 Forum Points

Engage in the Beat The GMAT forums to earn
100 points for $49 worth of Veritas practice GMATs FREE VERITAS PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote ## OG 13 30 ##### This topic has 4 expert replies and 0 member replies ## Timer 00:00 ## Your Answer A B C D E ## Global Stats Difficult The 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?

1. The gift certificates sold by the store yesterday were worth a total of between $1650 and$1800.
2. Yesterday the store sold more than 15 gift certificates worth $100 each. Answer: A Please explain why A is sufficient when there could have been a range between$1650 and $1800. ### GMAT/MBA Expert Legendary Member Joined 14 Jan 2015 Posted: 2666 messages Followed by: 125 members Upvotes: 1153 GMAT Score: 770 oquiella wrote: The 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?

1. The gift certificates sold by the store yesterday were worth a total of between $1650 and$1800.
2. Yesterday the store sold more than 15 gift certificates worth $100 each. Answer: A Please explain why A is sufficient when there could have been a range between$1650 and $1800. The key here is to recognize that we have a total of 20 gift certificates and that the number of gift certificates of each type must be an integer value. Say the store sold 17 of$100 certificates and 3 of the $10. That would give us 17*100 + 3*10 = 1730. That's between 1650 and 1800, so that's one possible scenario. Now let's see if anything else can work. What if there were 18 of the$100 certificates and 2 of the $10? That gives us a total of 1820 -not between 1650 and 1820 so this not a possibility that satisfies the statement. What if there were 16 of the$100 certificates and 4 of the $10? That gives us a total of 1640 - not between 1650 and 1800, so we can't use this scenario either. The only possibility that satisfies the statement is that there were 17 of the$100 certificates and 3 of the $10 certificates. So the answer is A _________________ Veritas Prep | GMAT Instructor Veritas Prep Reviews Save$100 off any live Veritas Prep GMAT Course

Enroll in a Veritas Prep GMAT class completely for FREE. Wondering if a GMAT course is right for you? Attend the first class session of an actual GMAT course, either in-person or live online, and see for yourself why so many students choose to work with Veritas Prep. Find a class now!

### GMAT/MBA Expert

Legendary Member Joined
14 Jan 2015
Posted:
2666 messages
Followed by:
125 members
1153
GMAT Score:
770
oquiella wrote:
The 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? 1. The gift certificates sold by the store yesterday were worth a total of between$1650 and $1800. 2. Yesterday the store sold more than 15 gift certificates worth$100 each.

Please explain why A is sufficient when there could have been a range between $1650 and$1800.
Algebraically, we can say that 'x' is the number of $10 certificates and '20-x' is the number of$100 certificates. (Because we know there are 20 total.) We know that 10x + 100(20-x) is the total value of the certificates. 10x + 100(20-x) = 10x + 2000 - 100x = 2000 - 90x. We know this value is between 1650 and 1800. Now test x's.

x = 1 --> 2000 - 90 = 1910. Nope
x = 2 --> 2000 - 180 = 1820. Nope
x=3 ---> 2000 - 270 = 1730. Satisfies!
x = 4 ---> 2000 - 360 = 1640. Nope

Only one value works, so we know that x = 3.

_________________
Veritas Prep | GMAT Instructor

Veritas Prep Reviews
Save $100 off any live Veritas Prep GMAT Course Enroll in a Veritas Prep GMAT class completely for FREE. Wondering if a GMAT course is right for you? Attend the first class session of an actual GMAT course, either in-person or live online, and see for yourself why so many students choose to work with Veritas Prep. Find a class now! ### GMAT/MBA Expert Elite Legendary Member Joined 23 Jun 2013 Posted: 10197 messages Followed by: 497 members Upvotes: 2867 GMAT Score: 800 Hi All, We're told that the only gift certificates that a certain store sold yesterday were worth either$100 each or $10 each and the store sold a total of 20 gift certificates yesterday. We're asked for the number of gift certificates worth$10 each that the store sold yesterday. This question can be solved with a bit of 'brute force' and some basic arithmetic.

To start, since we have just 20 gift certificates, we can list out a few of the possibilities and look for a pattern.
There could be...
20 $10 certificates and 0$100 certificates = (20)($10) + (0)($100) = $200 19$10 certificates and 1 $100 certificates = (19)($10) + (1)($100) =$290
18 $10 certificates and 2$100 certificates = (18)($10) + (2)($100) = $380 17$10 certificates and 3 $100 certificates = (17)($10) + (3)($100) =$470

For every $10 certificate that is changed to a$100 certificate, the total value of the 20 certificates increases by $90 (and you can use this pattern to go 'in reverse' from 20$100 certificates on down).

1) The gift certificates sold by the store yesterday were worth a total of between $1650 and$1800.

Based on the pattern defined above, the total could be...
$2000,$1910, $1820,$1730, $1640, etc. Only one of these values is between$1650 and $1800 though -$1730 (3 $10s and 17$100s).
Fact 1 is SUFFICIENT

2. Yesterday the store sold more than 15 gift certificates worth $100 each. With Fact 2, there are several possible outcomes, including$2000 (0 $10s and 20$100s) and $1920 (1$10 and 19 $100s). Fact 2 is INSUFFICIENT Final Answer: A GMAT assassins aren't born, they're made, Rich ### GMAT/MBA Expert GMAT Instructor Joined 09 Apr 2015 Posted: 1465 messages Followed by: 19 members Upvotes: 39 oquiella wrote: The 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?

1. The gift certificates sold by the store yesterday were worth a total of between $1650 and$1800.
2. Yesterday the store sold more than 15 gift certificates worth $100 each. We can let h = the number$100 gift certificates sold and t = the number of $10 gift certificates sold. Thus, we have h + t = 20, and we need to determine the value of t. Statement One Alone: The gift certificates sold by the store yesterday were worth a total of between$1650 and $1800. We see that number of$100 gift certificates sold is no more than 17. That is, h ≤ 17.

If h = 17, then t = 3, and the total value of the gift certificates is 17(100) + 10(3) = $1730, which is between$1650 and $1800. If h = 16, then t = 4, and the total value of the gift certificates is 16(100) + 10(4) =$1640. However, this is between not $1650 and$1800. Also, we don’t have to go any further down for the value of h, since we can see that from this point that there is no way the total value is between $1650 and$1800.

Therefore, we see that h must be 17 and t must be 3. Statement one alone is sufficient to answer the question.

Statement Two Alone:

Yesterday the store sold more than 15 gift certificates worth $100 each. We see that h > 15, so h could be 16, 17, 18, 19 or 20 and t could be 4, 3, 2, 1, or 0, respectively. Since we don’t have a unique value for t, statement two alone is sufficient to answer the question. Answer: A • FREE GMAT Exam Know how you'd score today for$0

Available with Beat the GMAT members only code

• 5 Day FREE Trial
Study Smarter, Not Harder

Available with Beat the GMAT members only code

• Magoosh
Study with Magoosh GMAT prep

Available with Beat the GMAT members only code

• 5-Day Free Trial
5-day free, full-access trial TTP Quant

Available with Beat the GMAT members only code

• Free Trial & Practice Exam
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

• Free Veritas GMAT Class
Experience Lesson 1 Live Free

Available with Beat the GMAT members only code

• Award-winning private GMAT tutoring
Register now and save up to \$200

Available with Beat the GMAT members only code

• Free Practice Test & Review
How would you score if you took the GMAT

Available with Beat the GMAT members only code

• Get 300+ Practice Questions

Available with Beat the GMAT members only code

• 1 Hour Free
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

### Top First Responders*

1 Ian Stewart 44 first replies
2 Brent@GMATPrepNow 33 first replies
3 Scott@TargetTestPrep 32 first replies
4 Jay@ManhattanReview 24 first replies
5 GMATGuruNY 18 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

### Most Active Experts

1 Scott@TargetTestPrep

Target Test Prep

149 posts
2 Max@Math Revolution

Math Revolution

93 posts
3 Ian Stewart

GMATiX Teacher

53 posts
4 Brent@GMATPrepNow

GMAT Prep Now Teacher

50 posts
5 GMATGuruNY

The Princeton Review Teacher

30 posts
See More Top Beat The GMAT Experts