Find all School-related info fast with the new School-Specific MBA Forum

It is currently 24 Jul 2014, 19:52

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

By using the numbers 1, 2, 3, 5 and 7 only once, how many

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
avatar
Joined: 28 Jan 2011
Posts: 24
Followers: 1

Kudos [?]: 2 [0], given: 15

By using the numbers 1, 2, 3, 5 and 7 only once, how many [#permalink] New post 06 Sep 2013, 12:54
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  25% (low)

Question Stats:

75% (02:30) correct 25% (01:36) wrong based on 59 sessions
By using the numbers 1, 2, 3, 5 and 7 only once, how many five digit numbers can be made that are divisible by 25?

(a) 10
(b) 11
(c) 12
(d) 13
(e) 14
[Reveal] Spoiler: OA

Last edited by Bunuel on 06 Sep 2013, 13:31, edited 1 time in total.
RENAMED THE TOPIC.
2 KUDOS received
Manager
Manager
avatar
Joined: 31 Jul 2013
Posts: 51
Location: United States
Concentration: General Management, Entrepreneurship
GPA: 3.6
WE: Law (Entertainment and Sports)
Followers: 1

Kudos [?]: 23 [2] , given: 4

Re: By using the numbers 1, 2, 3, 5 and 7 only once, how many [#permalink] New post 06 Sep 2013, 17:41
2
This post received
KUDOS
salsal wrote:
By using the numbers 1, 2, 3, 5 and 7 only once, how many five digit numbers can be made that are divisible by 25?

(a) 10
(b) 11
(c) 12
(d) 13
(e) 14


Given the restrictions, and divisibility by 25, we know that the last digit must be a 5 and the penultimate digit must be either 2 or 7. Setting out the digits in a row to think of possibilities, and going from right to left (most to least restrictive), we have 1 2 3 2 1. 1x2x3x2x1 = 12.

1 option for the last digit (5), 2 options for the penultimate digit (2 or 7), 3 then 2 then 1 option for the remaining 3 digits.
Expert Post
1 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 18729
Followers: 3240

Kudos [?]: 22363 [1] , given: 2615

Re: By using the numbers 1, 2, 3, 5 and 7 only once, how many [#permalink] New post 06 Sep 2013, 13:36
1
This post received
KUDOS
Expert's post
salsal wrote:
By using the numbers 1, 2, 3, 5 and 7 only once, how many five digit numbers can be made that are divisible by 25?

(a) 10
(b) 11
(c) 12
(d) 13
(e) 14


A number to be divisible by 25 must end with 00, 25, 50, or 75.

So, there are the following cases possible:

137-25 --> the first three digits can be arranged in 3=6 ways.
123-75 --> the first three digits can be arranged in 3=6 ways.

Total = 6 + 6 = 12.

Answer: C.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Manager
Manager
avatar
Joined: 17 Jul 2013
Posts: 101
Followers: 0

Kudos [?]: 1 [0], given: 64

Re: By using the numbers 1, 2, 3, 5 and 7 only once, how many [#permalink] New post 14 May 2014, 01:06
To solve this :
A number is divisible by 25 if the last two digits are multiple of 25 i.e 00, 25 , 50 or 75.

Hence from the given digits 7 or 2 must followed by 5.
number of ways we can select numbers of the first digit : 3 (1,3,7/2)
number of ways to select the second digit : 2 (since we can't repeat the digits)
third digit selected : 1
Fourth selection : 2 (2/7)
last digit must be 5 : 1

hence all selection is dependent we need to perform the product of all possible cases : 3*2*1*2*1 = 12
Re: By using the numbers 1, 2, 3, 5 and 7 only once, how many   [#permalink] 14 May 2014, 01:06
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic How many 6-digit number formed by 1,3,5,6,7,9 that is divisi glint09 1 15 Jul 2014, 02:15
10 Experts publish their posts in the topic If N=2^7*3^5*5^6*7^8. How many factors of N are divisible by GMATtracted 7 05 May 2013, 10:38
Using the numbers 1, 3, 5, 7 and 9, there are x 4-digit andrehaui 3 18 Apr 2007, 06:14
W is a set of numbers {1, 2, 3, 4, 5}. How many numbers less kdhong 5 06 Jan 2005, 10:38
12 Experts publish their posts in the topic If d=1/(2^3*5^7) is expressed as a terminating decimal, how mba4me 4 12 Sep 2004, 00:40
Display posts from previous: Sort by

By using the numbers 1, 2, 3, 5 and 7 only once, how many

  Question banks Downloads My Bookmarks Reviews Important topics  


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

Powered by phpBB © phpBB Group and phpBB SEO

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®.