GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 18 Jan 2019, 03:57

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.

Close

Request Expert Reply

Confirm Cancel
Events & Promotions in January
PrevNext
SuMoTuWeThFrSa
303112345
6789101112
13141516171819
20212223242526
272829303112
Open Detailed Calendar
  • Free GMAT Strategy Webinar

     January 19, 2019

     January 19, 2019

     07:00 AM PST

     09:00 AM PST

    Aiming to score 760+? Attend this FREE session to learn how to Define your GMAT Strategy, Create your Study Plan and Master the Core Skills to excel on the GMAT.
  • FREE Quant Workshop by e-GMAT!

     January 20, 2019

     January 20, 2019

     07:00 AM PST

     07:00 AM PST

    Get personalized insights on how to achieve your Target Quant Score.

How many 3-digit numbers can be formed so that the units place of a th

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

 
Intern
Intern
avatar
B
Joined: 06 Oct 2018
Posts: 16
Location: Oman
Concentration: Marketing, General Management
GMAT 1: 710 Q49 V38
GPA: 3.33
WE: Public Relations (Advertising and PR)
How many 3-digit numbers can be formed so that the units place of a th  [#permalink]

Show Tags

New post Updated on: 30 Oct 2018, 10:05
1
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 4 sessions

HideShow timer Statistics

How many 3-digit numbers can be formed so that the units place of a three-digit number is always prime? Repetition of digits is not allowed.

Can someone explain this with the 'fill in the blanks with number of available options' method?





OA: 256

Originally posted by manavivarma on 30 Oct 2018, 08:30.
Last edited by manavivarma on 30 Oct 2018, 10:05, edited 1 time in total.
Senior Manager
Senior Manager
User avatar
D
Joined: 22 Feb 2018
Posts: 416
CAT Tests
Re: How many 3-digit numbers can be formed so that the units place of a th  [#permalink]

Show Tags

New post 30 Oct 2018, 09:00
manavivarma wrote:
How many 3-digit numbers can be formed so that the units place of a three-digit number is always prime? Repetition of digits is not allowed.

Can someone explain this with the 'fill in the blanks with number of available options' method?


manavivarma

Can you update the options and OA in the question
_________________

Good, good Let the kudos flow through you

Intern
Intern
avatar
B
Joined: 06 Oct 2018
Posts: 16
Location: Oman
Concentration: Marketing, General Management
GMAT 1: 710 Q49 V38
GPA: 3.33
WE: Public Relations (Advertising and PR)
Re: How many 3-digit numbers can be formed so that the units place of a th  [#permalink]

Show Tags

New post 30 Oct 2018, 10:04
Princ there were no options to this question. Have updated the OA in my post though :)
Manager
Manager
avatar
G
Joined: 14 Jun 2018
Posts: 223
How many 3-digit numbers can be formed so that the units place of a th  [#permalink]

Show Tags

New post 30 Oct 2018, 10:07
1
8 * 8 * 4 = 256 ways
Prime no between 0-9 : 2 , 3 , 5 , 7
Total digits between 0-9 = 10
So unit digit can be filled in 4 ways
Now 9 digits remain. First slot cannot start with 0 otherwise it won't be a 3 digit number
So first slot can be filled in 8 ways.
Middle slot can have 0 so it can be filled in 8 ways.
Intern
Intern
avatar
B
Joined: 06 Oct 2018
Posts: 16
Location: Oman
Concentration: Marketing, General Management
GMAT 1: 710 Q49 V38
GPA: 3.33
WE: Public Relations (Advertising and PR)
Re: How many 3-digit numbers can be formed so that the units place of a th  [#permalink]

Show Tags

New post 30 Oct 2018, 10:09
Thanks pandeyashwin!
Manager
Manager
User avatar
S
Joined: 08 Sep 2008
Posts: 121
Location: India
Concentration: Operations, General Management
Schools: ISB '20
GPA: 3.8
WE: Operations (Transportation)
CAT Tests
Re: How many 3-digit numbers can be formed so that the units place of a th  [#permalink]

Show Tags

New post 30 Oct 2018, 10:22
Three Digit numbers from total 10 digit (0-10)
Restriction: Unit digit has to be prime. i.e. Either 2,3,5,or 7

Suppose three digit is A-B-C
Case 1: Unit digit 2:
We have 1 option for C (i.e.-2)=1
We have 8 option for A ( 1,3,4,5,6,7,8,9)=8
We have another 8 option for B (except 2 and digit taken by A)=8
So total 8*8*1=64 ( for unit digit 2)

we have total 4 cases.


64*4=256

Kudos if it helps...
_________________

Regards;
Vishal

+==========+
Kudos if it deserve....one...

Senior Manager
Senior Manager
User avatar
D
Joined: 22 Feb 2018
Posts: 416
CAT Tests
Re: How many 3-digit numbers can be formed so that the units place of a th  [#permalink]

Show Tags

New post 30 Oct 2018, 10:23
Thanks for updating OA

For units place, We have \(4\) choices i.e \(2,3,5,7\)
For hundreds place, We have \(8\) choices \([10(0 \quad to \quad 9)-1\)(Hundreds place cannot be \(0\))-\(1\)(Digit already used for units place)]
For Tens place, We have \(8\) choices \([10(0 \quad to \quad 9)-1\)(Digit already used for Hundreds place)-\(1\)(Digit already used for units place)]
Total Number of 3 digits such that units place of a the number is prime number and having distinct digits:\(8*8*4=256\)
_________________

Good, good Let the kudos flow through you

GMAT Club Bot
Re: How many 3-digit numbers can be formed so that the units place of a th &nbs [#permalink] 30 Oct 2018, 10:23
Display posts from previous: Sort by

How many 3-digit numbers can be formed so that the units place of a th

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.