It is currently 17 Nov 2017, 10:32

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If a, b are positive integers, is a/b a terminating decimal?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Expert Post
Math Revolution GMAT Instructor
User avatar
P
Joined: 16 Aug 2015
Posts: 4313

Kudos [?]: 3032 [0], given: 0

GPA: 3.82
Premium Member CAT Tests
If a, b are positive integers, is a/b a terminating decimal? [#permalink]

Show Tags

New post 12 Oct 2017, 01:47
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

70% (00:21) correct 30% (00:57) wrong based on 54 sessions

HideShow timer Statistics

If a, b are positive integers, is a/b a terminating decimal?

1) a is a multiple of 2
2) b is a factor of 10
[Reveal] Spoiler: OA

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Find a 10% off coupon code for GMAT Club members.
“Receive 5 Math Questions & Solutions Daily”
Unlimited Access to over 120 free video lessons - try it yourself
See our Youtube demo

Kudos [?]: 3032 [0], given: 0

Manager
Manager
User avatar
S
Joined: 05 Dec 2016
Posts: 223

Kudos [?]: 24 [0], given: 48

Concentration: Strategy, Finance
GMAT 1: 620 Q46 V29
GMAT ToolKit User
Re: If a, b are positive integers, is a/b a terminating decimal? [#permalink]

Show Tags

New post 12 Oct 2017, 02:30
For a/b to be a terminating decimal, b should have either 2 or 5 or both as its prime factors
(1) no information about b
(2) If b is a factor of 10, and 10 has 2 and 5 as its prime factors, then b can be 2;5;10 which means that a/b is a terminating decimal
Sufficient

Answer B.

Kudos [?]: 24 [0], given: 48

Expert Post
Math Revolution GMAT Instructor
User avatar
P
Joined: 16 Aug 2015
Posts: 4313

Kudos [?]: 3032 [0], given: 0

GPA: 3.82
Premium Member CAT Tests
If a, b are positive integers, is a/b a terminating decimal? [#permalink]

Show Tags

New post 16 Oct 2017, 07:13
Forget conventional ways of solving math questions. In DS, VA (Variable Approach) method is the easiest and quickest way to find the answer without actually solving the problem. Remember that equal number of variables and independent equations ensures a solution.

The first step of VA(Variable Approach) method is modifying the original condition and the question, and rechecking the number of variables and the number of equations.

The property that an irreducible fraction a/b is a terminating decimal depends on the denumerator only. When the denumerator of an irreducible only has 2 and 5 as prime factors, it is a terminating decimal.
Thus, only condition 2) is sufficient.
Therefore, B is the answer unlike our expectation.

Normally for cases where we need 2 more equations, such as original conditions with 2 variables, or 3 variables and 1 equation, or 4 variables and 2 equations, we have 1 equation each in both con 1) and con 2). Therefore, C has a high chance of being the answer, which is why we attempt to solve the question using 1) and 2) together. Here, there is 70% chance that C is the answer, while E has 25% chance. These two are the key questions. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer according to DS definition, we solve the question assuming C would be our answer hence using con 1) and con 2) together. (It saves us time). Obviously, there may be cases where the answer is A, B, D or E.

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Find a 10% off coupon code for GMAT Club members.
“Receive 5 Math Questions & Solutions Daily”
Unlimited Access to over 120 free video lessons - try it yourself
See our Youtube demo

Kudos [?]: 3032 [0], given: 0

If a, b are positive integers, is a/b a terminating decimal?   [#permalink] 16 Oct 2017, 07:13
Display posts from previous: Sort by

If a, b are positive integers, is a/b a terminating decimal?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.