• PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

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

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • 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
  • 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
  • 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
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • 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

If 3 < x < 100, for how many values of x is x/3 the sq

This topic has 3 expert replies and 2 member replies
rsarashi Master | Next Rank: 500 Posts Default Avatar
Joined
24 Dec 2016
Posted:
186 messages
Followed by:
2 members
Upvotes:
5

If 3 < x < 100, for how many values of x is x/3 the sq

Post Sat Apr 29, 2017 8:45 pm
If 3 < x < 100, for how many values of x is x/3 the square of a prime number?

(A) Two
(B) Three
(C) Four
(D) Five
(E) Nine

OAB

  • +1 Upvote Post
  • Quote
  • Flag
Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
Top Reply
Post Wed May 03, 2017 9:27 am
rsarashi wrote:
Quote:
2² = 4 and (3)(4) = 12. So, x = 12 meets the given conditions.
3² = 9 and (3)(9) = 27. So, x = 27 meets the given condition12
5² = 25 and (3)(25) = 75. So, x = 75 meets the given conditions.
7² = 49 and (3)(49) = 147. No good. We need values of x such that 3 < x < 100
Hi Brent ,

Thank you so much for your reply.

Just a quick question can you please advise that why did you multiply with 3? We have to divide x/3.

Please explain sir.
Great question.

First off, we want x/3 to be the square of a prime number.
Since all prime numbers are integers, the square of a prime number will be an integer.

In order for x/3 to be an integer, it must be the case that x is divisible by 3.
Another way to put it is that x must be a multiple of 3.
This why I took each squared value and multiplied it by 3.

Cheers,
Brent

_________________
Brent Hanneson – Founder of GMATPrepNow.com
Use our video course along with Beat The GMAT's free 60-Day Study Guide

Check out the online reviews of our course
Come see all of our free resources

  • +1 Upvote Post
  • Quote
  • Flag
Thanked by: rsarashi
GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months!
rsarashi Master | Next Rank: 500 Posts Default Avatar
Joined
24 Dec 2016
Posted:
186 messages
Followed by:
2 members
Upvotes:
5
Top Reply
Post Sat May 06, 2017 6:46 pm
Quote:
Great question.

First off, we want x/3 to be the square of a prime number.
Since all prime numbers are integers, the square of a prime number will be an integer.

In order for x/3 to be an integer, it must be the case that x is divisible by 3.
Another way to put it is that x must be a multiple of 3.
This why I took each squared value and multiplied it by 3.
Hi Brent ,

Perfect! All clear.

Thanks

  • +1 Upvote Post
  • Quote
  • Flag
Post Wed May 03, 2017 9:27 am
rsarashi wrote:
Quote:
2² = 4 and (3)(4) = 12. So, x = 12 meets the given conditions.
3² = 9 and (3)(9) = 27. So, x = 27 meets the given condition12
5² = 25 and (3)(25) = 75. So, x = 75 meets the given conditions.
7² = 49 and (3)(49) = 147. No good. We need values of x such that 3 < x < 100
Hi Brent ,

Thank you so much for your reply.

Just a quick question can you please advise that why did you multiply with 3? We have to divide x/3.

Please explain sir.
Great question.

First off, we want x/3 to be the square of a prime number.
Since all prime numbers are integers, the square of a prime number will be an integer.

In order for x/3 to be an integer, it must be the case that x is divisible by 3.
Another way to put it is that x must be a multiple of 3.
This why I took each squared value and multiplied it by 3.

Cheers,
Brent

_________________
Brent Hanneson – Founder of GMATPrepNow.com
Use our video course along with Beat The GMAT's free 60-Day Study Guide

Check out the online reviews of our course
Come see all of our free resources

  • +1 Upvote Post
  • Quote
  • Flag
Thanked by: rsarashi
GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months!
rsarashi Master | Next Rank: 500 Posts Default Avatar
Joined
24 Dec 2016
Posted:
186 messages
Followed by:
2 members
Upvotes:
5
Post Sat May 06, 2017 6:46 pm
Quote:
Great question.

First off, we want x/3 to be the square of a prime number.
Since all prime numbers are integers, the square of a prime number will be an integer.

In order for x/3 to be an integer, it must be the case that x is divisible by 3.
Another way to put it is that x must be a multiple of 3.
This why I took each squared value and multiplied it by 3.
Hi Brent ,

Perfect! All clear.

Thanks

  • +1 Upvote Post
  • Quote
  • Flag
rsarashi Master | Next Rank: 500 Posts Default Avatar
Joined
24 Dec 2016
Posted:
186 messages
Followed by:
2 members
Upvotes:
5
Post Wed May 03, 2017 9:19 am
Quote:
2² = 4 and (3)(4) = 12. So, x = 12 meets the given conditions.
3² = 9 and (3)(9) = 27. So, x = 27 meets the given condition12
5² = 25 and (3)(25) = 75. So, x = 75 meets the given conditions.
7² = 49 and (3)(49) = 147. No good. We need values of x such that 3 < x < 100
Hi Brent ,

Thank you so much for your reply.

Just a quick question can you please advise that why did you multiply with 3? We have to divide x/3.

Please explain sir.

  • +1 Upvote Post
  • Quote
  • Flag

Best Conversation Starters

1 lheiannie07 120 topics
2 LUANDATO 62 topics
3 swerve 62 topics
4 ardz24 61 topics
5 AAPL 57 topics
See More Top Beat The GMAT Members...

Most Active Experts

1 image description Scott@TargetTestPrep

Target Test Prep

174 posts
2 image description Brent@GMATPrepNow

GMAT Prep Now Teacher

173 posts
3 image description Rich.C@EMPOWERgma...

EMPOWERgmat

131 posts
4 image description Jeff@TargetTestPrep

Target Test Prep

130 posts
5 image description EconomistGMATTutor

The Economist GMAT Tutor

130 posts
See More Top Beat The GMAT Experts