GRE Official Guide Question Directory
close

It is currently 23 Nov 2020, 10:41
Search
Register
My Tests
New posts
Unanswered

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Go to My Workbook Learn more
CLICK HERE TO HIDE/SHOW EVENTS

In sequence Q, the first number is 3, and each subsequent nu

  Question banks Downloads My Bookmarks Reviews Important topics  
 
Search for:
 
Print view
First unread post
Author Message
TAGS:
Retired Moderator
User avatar
Joined: 07 Jun 2014
Posts: 4803
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 175

Kudos [?]: 3028 [0], given: 394

In sequence Q, the first number is 3, and each subsequent nu [#permalink] New post 30 Jul 2018, 10:16
Expert's post
00:00

Question Stats:

83% (01:08) correct 16% (01:25) wrong based on 24 sessions
In sequence Q, the first number is 3, and each subsequent number in the sequence is determined by doubling the previous number and then adding 2. In the first 10 terms of the sequence, how many times does the digit 8 appear in the units digit?

[Reveal] Spoiler: OA
9

_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

1 KUDOS received
Moderator
Moderator
User avatar
Joined: 07 Jan 2018
Posts: 697
Followers: 11

Kudos [?]: 785 [1] , given: 88

Re: In sequence Q, the first number is 3, and each subsequent nu [#permalink] New post 31 Jul 2018, 06:59
1
This post received
KUDOS
From the question stem:
The first term is 3
The second term is 3*2 + 2 = 8
The third term is 8*2 + 2 = 18

We can see that when the unit digit 8 is multiplied by 2 it ends with 6 and when 2 is added it becomes 8 hence all the terms except the first have their units digit as 8. In total there are 9 such terms
_________________

Need Practice? 20 Free GRE Quant Tests available for free with 20 Kudos

Retired Moderator
User avatar
Joined: 07 Jun 2014
Posts: 4803
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 175

Kudos [?]: 3028 [0], given: 394

Re: In sequence Q, the first number is 3, and each subsequent nu [#permalink] New post 12 Aug 2018, 07:04
Expert's post
Explanation

After the first term in the sequence, every term has a units digit of 8:

\(Q_1 = 3\)
\(Q_2 = 2(3) + 2 = 8\)
\(Q_3 = 2(8) + 2 = 18\)
\(Q_4 = 2(18) + 2 = 38\)
\(Q_5 = 2(38) + 2 = 78\)
…

So 8 is the units digit nine out of the first ten times.
_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

Re: In sequence Q, the first number is 3, and each subsequent nu   [#permalink] 12 Aug 2018, 07:04
Display posts from previous: Sort by

In sequence Q, the first number is 3, and each subsequent nu

  Question banks Downloads My Bookmarks Reviews Important topics  
Print view
First unread post

Moderators: GreenlightTestPrep, theBrahmaTiger, amorphous, BrushMyQuant, AskMathQuestions, gajala, pranab223, Moderators

Search for:


cron

GRE Prep Club Forum Home| About| Terms and Conditions and Privacy Policy| GRE Prep Club Rules| Contact

Powered by phpBB © phpBB Group

Kindly note that the GRE® test is a registered trademark of the Educational Testing Service®, and this site has neither been reviewed nor endorsed by ETS®.

Main navigation

Partners

GRE Resources

www.ets.org/gre