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

OG 12 unit problem

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Source: — Problem Solving |
Legendary Member
Posts: 610
Joined: Fri Jan 15, 2010 12:33 amFollowed by: 2 members
Thanked: 47 times

by kstv » Wed Jun 02, 2010 3:26 am
pradeepkaushal9518 wrote:what is the unit digit of (13)^4(17)^2(29)^3?

A.9
B.7
C.5
D.3
E.1

plz give the best way to find out the unit digit
just consider the unit digits
(3^4) *(7^2) *(9^3)
Even while calculating 3^4 , notice that the unit digit is 3*3 = 9*3 = ..7*3=..1
7^2 = 49
29^3 = 9*9 = 81*9=..9
now 1*9*9 = ...1
Top
Join the discussion
User avatar
GMAT Instructor
Posts: 1052
Joined: Fri May 21, 2010 1:30 amFollowed by: 98 members
Thanked: 335 times

by Patrick_GMATFix » Wed Jun 02, 2010 8:35 am
kstv's explanation is the best way to solve this Q. You know there is no way you can be expected to calculate the number. Since the units digit of a product depends only on the units digit of each term in the multiplication, we can just focus on the units digit of each term. In general, if I'm stuck on pattern problems, I start solving manually until I see the pattern develops.

This is OG12 Problem solving #190. OG Companion 12th Solution is attached.

-Patrick
You do not have the required permissions to view the files attached to this post.
  • Ask me about tutoring.
Top
Join the discussion
GMAT Instructor
Posts: 1302
Joined: Mon Oct 19, 2009 2:13 pmFollowed by: 164 members
Location: Toronto
Thanked: 539 times
GMAT Score:800

by Testluv » Wed Jun 02, 2010 9:43 pm
yep.

The units digit of sequential integer powers of a given base follows a cyclic pattern.

For example:

3^1 = 3
3^2 = 9
3^3 = ...7
3^4 = ...1

3^5 = ....3 (again!)

So, the 1st, 5th, 9th, 13th, etc powers of 3 result in units digit of 3.
Likewise, the 2nd, 6th, 10th, 14th etc powers of 3 result in units digit of 9.
And so on.
Kaplan Teacher in Toronto
Top
Join the discussion