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

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

tough number properties

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Master | Next Rank: 500 Posts
Posts: 100
Joined: Wed Jul 30, 2008 9:52 am
Thanked: 4 times
by ashish1354 » Tue Sep 23, 2008 3:37 am
How many integers less than 1000 have no factors (other than 1) in common with 1000?

my question is whether we need to consider integers starting from 0 till 999

& if we do do we need to include 0??
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
User avatar
Master | Next Rank: 500 Posts
Posts: 316
Joined: Mon Sep 22, 2008 12:04 amFollowed by: 1 member
Thanked: 36 times

by Morgoth » Tue Sep 23, 2008 4:00 am
I guess you have to consider 0. Since 0 is a factor of no number and multiple of every number.

But on GMAT you generally get things like positive integers or positive factors in the question stem itself. So, you dont have to consider 0 then.

0 is an integer neither positive nor negative.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 2623
Joined: Mon Jun 02, 2008 3:17 amFollowed by: 355 members
Location: Montreal
Thanked: 1090 times
GMAT Score:780

Re: tough number properties

by Ian Stewart » Tue Sep 23, 2008 5:42 am
ashish1354 wrote:How many integers less than 1000 have no factors (other than 1) in common with 1000?

my question is whether we need to consider integers starting from 0 till 999

& if we do do we need to include 0??
If the question simply says 'How many integers less than 1000', you'd even need to consider negative numbers, so the answer would be 'an infinite number'. You won't see a question like that on the GMAT- if you saw such a question, it would say 'positive integers', in which case you would not, of course, consider zero, since zero is not positive.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

ianstewartgmat.com
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 891
Joined: Sat Aug 16, 2008 4:21 amFollowed by: 1 member
Thanked: 27 times
GMAT Score:660(

by 4meonly » Tue Sep 23, 2008 5:55 am
What is the answer?
400?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 105
Joined: Tue Jul 15, 2008 7:03 pm
Thanked: 5 times

by pre-gmat » Tue Sep 23, 2008 2:32 pm
Yeah I guess answer should be 400.

here's my reasoning...

1000 has 2,5 as prime factors.

so first eliminate all even numbers which leaves 500 odd integers and now out of 500 eliminate any number divisible by 5 which is 100 and therefore leaves us with 400.
We haev already covered the case of 2 and 5 together being factor.


Let me know the OA.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1