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 →

Multiple of 8

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Newbie | Next Rank: 10 Posts
Posts: 6
Joined: Wed Sep 09, 2009 11:44 am
by rafodr » Wed Sep 16, 2009 8:50 am
Please help with this one...

If x and y are positive integers, is xy a multiple of 8?

(1) The greatest common divisor of x and y is 10
(2) The least common multiple of x and y is 100

I thought that A was the answer, but it says that the answer is C
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Data Sufficiency |

GMAT/MBA Expert

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

Re: Multiple of 8

by Brent@GMATPrepNow » Wed Sep 16, 2009 9:48 am
rafodr wrote:Please help with this one...

If x and y are positive integers, is xy a multiple of 8?

(1) The greatest common divisor of x and y is 10
(2) The least common multiple of x and y is 100

I thought that A was the answer, but it says that the answer is C
The answer is C.
(1) INSUFFICIENT - two conflicting sets of values:
a) x=10, y=10 xy is not divisible by 8
b) x=20, y=10 xy is divisible by 8

(2) INSUFFICIENT - two conflicting sets of values:
a) x=100, y=10 xy is divisible by 8
b) x=25, y=4 xy is not divisible by 8

(1)&(2)
(1) tells us that x and y both have a 2 and a 5 in their prime factorizations.
(2) tell us that, in addition to the 2 and 5 that x and y share in their prime factorizations, one of the values has an additional 2 in its prime factorization and the other has an addditional 5.

To solve this question(and understant my solution :-), it is useful to know the systematic approach to finding GCD and LCM. I have created a video tutorial at https://www.leapeducation.ca/gcd-lcm.mp4
You might want to review this video to better understand my reasoning above.
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 157
Joined: Tue Oct 07, 2008 5:47 am
Thanked: 3 times

by PussInBoots » Wed Sep 16, 2009 12:15 pm
Remember formula: x*y = GCF(x,y) * LCM(x,y) (ManhattanGMAT)
xy = 1000, clearly divisible by 8.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1