• Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • e-gmat Exclusive Offer
    Get 300+ Practice Questions
    25 Video lessons and 6 Webinars for FREE

    Available with Beat the GMAT members only code

    MORE DETAILS
    e-gmat Exclusive Offer
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • Target Test Prep
    5-Day Free Trial
    5-day free, full-access trial TTP Quant

    Available with Beat the GMAT members only code

    MORE DETAILS
    Target Test Prep
  • Kaplan Test Prep
    Free Practice Test & Review
    How would you score if you took the GMAT

    Available with Beat the GMAT members only code

    MORE DETAILS
    Kaplan Test Prep
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • Varsity Tutors
    Award-winning private GMAT tutoring
    Register now and save up to $200

    Available with Beat the GMAT members only code

    MORE DETAILS
    Varsity Tutors
  • Economist Test Prep
    Free Trial & Practice Exam
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep

Question 20, section 17 of "lots of DS questions"

This topic has 1 expert reply and 3 member replies
isisalaska Community Manager Default Avatar
Joined
10 Dec 2006
Posted:
363 messages
Followed by:
2 members
Thanked:
7 times

Question 20, section 17 of "lots of DS questions"

Post Tue Feb 13, 2007 1:00 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    Please explain this question

    20. Is 5^k less than 1,000 ?
    (1) 5^k-1>3000
    (2) 5^k-1=5^k-500

    B

    _________________
    Isis Alaska

    Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
    Neo2000 Legendary Member
    Joined
    27 Jan 2007
    Posted:
    519 messages
    Thanked:
    31 times
    Test Date:
    30/09
    Target GMAT Score:
    710
    Post Tue Feb 13, 2007 9:07 pm
    Can be answered using statement 2 alone

    5^k -5^(k-1) = 500
    By Law of Indices a^(m-n) = (a^m)/(a^n)

    5^(k-1)(5 -1) = 500
    4(5^(k-1)) = 500

    Simplify to get value of k

    amitamit2020 Junior | Next Rank: 30 Posts Default Avatar
    Joined
    24 Jan 2007
    Posted:
    17 messages
    Post Wed Feb 14, 2007 3:23 am
    I agree with Neo2000 that (2) is necessary and sufficient condiction to answer the quaestion. However stateembnt (1) can also provide sufficinet and necessary condiction to answer tha question because 5^(k-1) > 3000 means 5^k > 15000 > 1000, thus 5^k > 100. so the coreect answer to the quastion shoul be (D) rather than (B).

    Pl. correct my understanding if found erronious.

    banona Senior | Next Rank: 100 Posts Default Avatar
    Joined
    30 Dec 2006
    Posted:
    38 messages
    Thanked:
    1 times
    Post Wed Feb 14, 2007 7:34 am
    Hi,
    I agree with amitamit2020 ; Answer should be D
    Otherwise, check if expressions are as written in the original question and look at the source;

    GMAT/MBA Expert

    Stacey Koprince GMAT Instructor
    Joined
    27 Dec 2006
    Posted:
    2228 messages
    Followed by:
    679 members
    Thanked:
    639 times
    GMAT Score:
    780
    Post Wed Feb 14, 2007 8:05 pm
    This is an OG question that has not been copied correctly (#131 in 11th edition).

    Should be:

    Is 5^k less than 1,000?
    (1) 5^(k+1) > 3,000
    (2) 5^(k-1) = (5^k) - 500

    As I just wrote it above, the OA is B.

    _________________
    Please note: I do not use the Private Messaging system! I will not see any PMs that you send to me!!

    Stacey Koprince
    GMAT Instructor
    Director of Online Community
    Manhattan GMAT

    Contributor to Beat The GMAT!

    Learn more about me

    Free Manhattan Prep online events - The first class of every online Manhattan Prep course is free. Classes start every week.

    Best Conversation Starters

    1 Vincen 152 topics
    2 lheiannie07 61 topics
    3 Roland2rule 49 topics
    4 LUANDATO 44 topics
    5 ardz24 40 topics
    See More Top Beat The GMAT Members...

    Most Active Experts

    1 image description Brent@GMATPrepNow

    GMAT Prep Now Teacher

    140 posts
    2 image description Rich.C@EMPOWERgma...

    EMPOWERgmat

    110 posts
    3 image description EconomistGMATTutor

    The Economist GMAT Tutor

    109 posts
    4 image description GMATGuruNY

    The Princeton Review Teacher

    107 posts
    5 image description DavidG@VeritasPrep

    Veritas Prep

    72 posts
    See More Top Beat The GMAT Experts