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

Redeem

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.

★★★★★5.0559 reviews
GMATLiveTeach 7 seats left
Chris Peckover
NEXT LIVE COHORT

Oct 13 to Jan 7, 2027

with Chris Peckover

Schedule
Tue, Thu · 8:00 to 10:00 PM ET
Included
40 live hours + 6 months of GMAT OnDemand
  • Live instruction and real-time questions
  • Class recordings and assigned practice
View class & enroll
Limited cohort · enrollment openTarget Test Prep
EALiveTeach 5 seats left
Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

Schedule
Sun · 9:30 AM to 12:30 PM ET
Included
Live EA class + 6 months of EA OnDemand
  • Expert-led weekly online sessions
  • EA Masterclass access between classes
View EA class & enroll
Limited cohort · enrollment openTarget Test Prep
GMATOnDemand Start anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

130-point score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 559 reviewsTarget Test Prep

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

Probability

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Legendary Member
Posts: 1132
Joined: Mon Jul 20, 2009 3:38 amFollowed by: 6 members
Location: India
Thanked: 64 times
GMAT Score:760
by harsh.champ » Tue Feb 09, 2010 5:08 am
Suppose that a and b are two integers, not necessarily distinct, chosen from the set S = 1, 2, 3, · · · , 200. What is the probability that the unit digit of 3a + 7b is 6"Œ?

(A)5/16
(B)3/16
(C)3/17
(D)7/17
(E)3/13

The OA is B.
It takes time and effort to explain, so if my comment helped you please press Thanks button :)



Just because something is hard doesn't mean you shouldn't try,it means you should just try harder.

"Keep Walking" - Johnny Walker :P
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
User avatar
Legendary Member
Posts: 1022
Joined: Mon Jul 20, 2009 11:49 pmFollowed by: 2 members
Location: Gandhinagar
Thanked: 41 times

by shashank.ism » Tue Feb 09, 2010 5:16 am
harsh.champ wrote:Suppose that a and b are two integers, not necessarily distinct, chosen from the set S = 1, 2, 3, · · · , 200. What is the probability that the unit digit of 3a + 7b is 6"Œ?

(A)5/16
(B)3/16
(C)3/17
(D)7/17
(E)3/13

The OA is B.
Consider the powers of 3 and 7 mod 10.
Thus there are 16 pairs of value of 3a and 7b mod 10. They are (3,7), (3,9), (3,3), (3,1), (9,7), (9,9), (9,3), (9,1), (7,7), (7,9), (7,3), (7,1), (1,7), (1,9), (1,3), (1,1)
Of these only 3 have a sum which is 6 mod 10, namely (3,3), (9,7) and (7,9).
Thus the probability is 3/16
[spoiler](B)[/spoiler] is the correct
My Websites:
www.mba.webmaggu.com - India's social Network for MBA Aspirants

www.deal.webmaggu.com -India's online discount, coupon, free stuff informer.

www.dictionary.webmaggu.com - A compact free online dictionary with images.

Nothing is Impossible, even Impossible says I'm possible.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 1275
Joined: Thu Sep 21, 2006 11:13 pmFollowed by: 2 members
Location: Arabian Sea
Thanked: 125 times

by ajith » Tue Feb 09, 2010 6:38 am
harsh.champ wrote:Suppose that a and b are two integers, not necessarily distinct, chosen from the set S = 1, 2, 3, · · · , 200. What is the probability that the unit digit of 3a + 7b is 6"Œ?

(A)5/16
(B)3/16
(C)3/17
(D)7/17
(E)3/13

The OA is B.
Is it 3^a+7^b or 3a+7b?
Always borrow money from a pessimist, he doesn't expect to be paid back.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1