Live GMAT classes with Target Test Prep start Nov 21 and Nov 22. First class free.

See classes
Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

Newsweek Readers’ Choice Awards 2026 winner: Target Test Prep, #1 Test Prep

Target Test Prep was voted #1 Best Test Prep in the 2026 Newsweek Readers’ Choice™ Awards.

★★★★★5.0563 reviews
GMATLiveTeachStarts Nov 22
Josh Braslow, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Josh Braslow, 20+ years in test prep

Nov 22 · Josh Braslow
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemandStart anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

EXECUTIVE ASSESSMENT

with

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemandStart anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 563 reviewsTarget Test Prep

Probability Question

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Newbie | Next Rank: 10 Posts
Posts: 1
Joined: Mon Feb 22, 2010 9:48 am
by thashadow » Wed Nov 03, 2010 8:24 am
Hey guys, long time reader, first time poster. I couldn't figure this one out, so of course I come to you guys to walk me through the steps. Have a go at it.

X - {1,2,3,4,5}
Y - {1,2,3,4,5}

Randomly pick one number from Set x, and one number from set Y

What is the probability that the product of x and y is less than 10?


Thanks
-L
Top
Join the discussion
Source: — Problem Solving |

GMAT/MBA Expert

GMAT Instructor
Posts: 1179
Joined: Sun Apr 11, 2010 9:07 pmFollowed by: 88 members
Location: Milpitas, CA
Thanked: 447 times

by Rahul@gurome » Wed Nov 03, 2010 9:10 am
thashadow wrote:Hey guys, long time reader, first time poster. I couldn't figure this one out, so of course I come to you guys to walk me through the steps. Have a go at it.

X - {1,2,3,4,5}
Y - {1,2,3,4,5}

Randomly pick one number from Set x, and one number from set Y

What is the probability that the product of x and y is less than 10?


Thanks
-L
Total number of possible pairs = 5 + 5 + 5 + 5 + 5 = 25

Total number of pairs such that, xy < 10:
  • (1) x = 1, y can be 1, 2, 3, 4 or 5 --> 5 ways
    (2) x = 2, y can be 1, 2, 3 or 4 --> 4 ways
    (3) x = 3, y can be 1, 2 or 3 --> 3 ways
    (4) x = 4, y can be 1 or 2 --> 2 ways
    (5) x = 5, y can be 1 --> 1 way
Thus a total of = 5 + 4 + 3 + 2 + 1 = 15 ways.

Therefore, required probability = 15/25 = 3/5
Rahul Lakhani
Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)
Top
Join the discussion
Junior | Next Rank: 30 Posts
Posts: 17
Joined: Thu Jun 24, 2010 3:56 am
Thanked: 3 times

by gtestprep » Wed Nov 03, 2010 9:16 am
So let's assume there are 2 slots that need to be filled up such that the first slot is always filled with a number from Set X and the second slot from Set Y. If you selected 1 from Set X, then there are 5 ways to select an element from Set Y such that the product of the numbers is less than 10. So, there are 5 ways of doing this ( 1*1, 1*2, 1*3, 1*4 and 1*5 )

Likewise, if you selected 2 from Set X, then there are 4 ways to select an element from Set Y (remember 2 * 5 = 10) There are 4 ways of doing this ( 2*1, 2*2, 2*3 and 2*4 )

Similarly, if 3, 4 and 5 are selected from Set X, there are 3, 2 and 1 ways respectively (such that the product is less than 10)

Therefore, the total number of ways of selecting elements from set X & Y such that the product of both the elements is less than 10 is the sum of the individual possibilities as stated above. i.e. 5 + 4 + 3 + 2 + 1 = 15

The total number of ways of selecting the numbers though is 5 from set X and 5 from set Y. So, there are 25 total ways of selecting numbers.

The probability is 15/25 = 3/5

HTH
Top
Join the discussion