Welcome! Check out our free B-School Guides to learn how you compare with other applicants.
Login or Register
 

no. of integers divisible

This topic has 4 member replies
Bookmark
Previous Topic Next Topic
cypherskull Rising GMAT Star
Joined
31 Mar 2012
Posted:
94 messages
Thanked:
8 times
Test Date:
29th August, 2012
no. of integers divisible Post Mon May 07, 2012 1:18 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    How many positive integers between 200 and 300 (both inclusive) are not divisible by 2, 3 or 5?

    A. 3

    B. 16

    C. 75

    D. 24

    E. 26

    _________________
    Regards,
    Sunit

    ________________________________

    Kill all my demons..And my angels might die too!

    Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
    aneesh.kg GMAT Destroyer!
    Joined
    16 Apr 2012
    Posted:
    382 messages
    Followed by:
    23 members
    Thanked:
    174 times
    Post Mon May 07, 2012 1:38 pm
    There are 101 integers from 200 to 300.
    The 51 integers that are even will be divisible by 2. Exclude them.
    50 remaining.
    How many odd multiples of 3 are there?
    Starting from 201 to 297, there are 17 such integers. (Use AP formula: last term = a
    + (n - 1)*d to count). Exclude them.
    33 remaining.
    How many multiples of 5 are neither divisible for 2 nor 3. 205, 215, 235, 245, 265, 275, 295.
    7 such numbers. Exclude them too.
    26 remaining.

    (E) is the answer.

    _________________
    Aneesh Bangia
    GMAT Math Coach
    aneesh.bangia@gmail.com

    GMATPad:
    Facebook Page: http://www.facebook.com/GMATPad

    satyavegi Just gettin' started! Default Avatar
    Joined
    13 Aug 2011
    Posted:
    14 messages
    Post Wed May 09, 2012 11:17 pm
    Can you please explain the concept on how to tackle this kind of questions ..

    general mistakes we do here are counting twice or sometimes taking as 100 numbers as in between instead of 101.

    can you brief this area

    thanks

    aneesh.kg GMAT Destroyer!
    Joined
    16 Apr 2012
    Posted:
    382 messages
    Followed by:
    23 members
    Thanked:
    174 times
    Post Wed May 09, 2012 11:42 pm
    Oh yes.

    Read this:
    http://www.beatthegmat.com/finding-the-sum-of-consecutive-integers-t111715.html#470942

    This will you help you reduce your mistakes in counting.
    In this question, however, you've to be a little careful about which numbers have already been considered. for e.g. when the multiples of 5 had to be counted, one had to be really careful to rule out the multiples of 2 (210, 220,..) and multiples of 3 (such as 225, 255, 285) because they had already been counted.

    _________________
    Aneesh Bangia
    GMAT Math Coach
    aneesh.bangia@gmail.com

    GMATPad:
    Facebook Page: http://www.facebook.com/GMATPad

    amit28it Rising GMAT Star Default Avatar
    Joined
    04 Nov 2011
    Posted:
    82 messages
    Followed by:
    1 members
    Post Thu May 10, 2012 12:14 am
    The answer calculated by aneesh.kg is absolutely correct not only the answer but the method used is also the simplest one and my answer is exactly the same that is E.
    online tutor

    Best Conversation Starters
    1 varun289 38 topics
    2 killerdrummer 22 topics
    3 sana.noor 20 topics
    4 sanaa.rizwan 14 topics
    5 guerrero 14 topics
    See More Top Beat The GMAT Members...

    Most Active Experts
    1 image description Brent@GMATPrepNow

    GMAT Prep Now Teacher

    		 204 posts
    2 image description GMATGuruNY

    The Princeton Review Teacher

    		 136 posts
    3 image description Jim@StratusPrep

    Stratus Prep

    		 100 posts
    4 image description Anju@Gurome

    Gurome

    		 74 posts
    5 image description Jon@Admissionado

    Admissionado

    		 51 posts
    See More Top Beat The GMAT Experts