BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Factor

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Legendary Member
Posts: 643
Joined: Wed Aug 14, 2013 4:27 am
Thanked: 48 times
Followed by:7 members

Factor

by vinay1983 » Tue Aug 27, 2013 6:18 am
What are the different ways to solve such problems?
Attachments
OG 13.jpg
You can, for example never foretell what any one man will do, but you can say with precision what an average number will be up to!
Top
Source: — Data Sufficiency |
User avatar
MBA Admissions Consultant
Posts: 2279
Joined: Fri Nov 11, 2011 7:51 am
Location: New York
Thanked: 660 times
Followed by:266 members
GMAT Score:770

by Jim@StratusPrep » Tue Aug 27, 2013 8:19 am
B

Only the denominator matters. If the denominator contains factors of only 2 and 5 it is terminating.
GMAT Answers provides a world class adaptive learning platform.
-- Push button course navigation to simplify planning
-- Daily assignments to fit your exam timeline
-- Organized review that is tailored based on your abiility
-- 1,000s of unique GMAT questions
-- 100s of handwritten 'digital flip books' for OG questions
-- 100% Free Trial and less than $20 per month after.
-- Free GMAT Quantitative Review

Image
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Tue Aug 27, 2013 8:32 am
If r and s are positive integers, can the fraction r/s be expressed as a decimal with only a finite number of non-zero digits?
(1) s is a factor of 100.
(2) r is a factor of 100.
IN OTHER WORDS, is decimal version of r/s a terminating decimal?

Aside: A terminating decimal is one that does not repeat.
For example, 1/4 = 0.25 so this is a terminating decimal.
Conversely, 1/3 = 0.333333.... so this is a non-terminating decimal

Target question: Is r/s a terminating decimal?

Statement 1: r is a factor of 100
There are several pairs of values that meet this condition. Here are two:
Case a: r = 1 and s = 4, in which case r/s is a terminating decimal
Case b: r = 1 and s = 3, in which case r/s is not a terminating decimal
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: s is a factor of 100
There's a nice rule that says something like,
If the prime factorization of the denominator contains only 2's and/or 5's, then the decimal version of the fraction will be a terminating decimal.
Since 100 = 2x2x5x5, any factor of 100 will contain only 2's and/or 5'2 (or the denominator can be 1, in which case the decimal will definitely terminate).
Since the denominator of r/s must contain only 2's and/or 5's, r/s must be a terminating decimal
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer = B

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Post new topic Post Reply
• Page 1 of 1