It is currently 19 Nov 2017, 03:53

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# If a and b are positive integers, what is the units digit of

Author Message
TAGS:

### Hide Tags

Director
Status: Verbal Forum Moderator
Joined: 17 Apr 2013
Posts: 602

Kudos [?]: 637 [2], given: 298

Location: India
GMAT 1: 710 Q50 V36
GMAT 2: 750 Q51 V41
GMAT 3: 790 Q51 V49
GPA: 3.3
If a and b are positive integers, what is the units digit of [#permalink]

### Show Tags

17 Jun 2014, 12:28
2
KUDOS
22
This post was
BOOKMARKED
00:00

Difficulty:

65% (hard)

Question Stats:

60% (01:09) correct 40% (01:04) wrong based on 424 sessions

### HideShow timer Statistics

If a and b are positive integers, what is the units digit of b ?

(1) b is 25% greater than a.

(2) If b is decreased by 50%, the result is not an integer.
[Reveal] Spoiler: OA

_________________

Like my post Send me a Kudos It is a Good manner.
My Debrief: http://gmatclub.com/forum/how-to-score-750-and-750-i-moved-from-710-to-189016.html

Last edited by Bunuel on 17 Jun 2014, 12:32, edited 1 time in total.
Edited the question

Kudos [?]: 637 [2], given: 298

Math Expert
Joined: 02 Sep 2009
Posts: 42246

Kudos [?]: 132650 [8], given: 12331

Re: If a and b are positive integers, what is the units digit of [#permalink]

### Show Tags

17 Jun 2014, 12:36
8
KUDOS
Expert's post
6
This post was
BOOKMARKED
If a and b are positive integers, what is the units digit of b ?

(1) b is 25% greater than a --> b=1.25a --> b/a = 5/4 --> b is a multiple of 5. So, the units digit of b could be 0 as well as 5. Not sufficient.

(2) If b is decreased by 50%, the result is not an integer --> b/2 is not an integer --> b is not even. Not sufficient.

(1)+(2) Since b is not even, then its units digit cannot be 0, thus from (1) its units digit must be 5. Sufficient.

Hope it's clear.
_________________

Kudos [?]: 132650 [8], given: 12331

Intern
Joined: 26 Aug 2014
Posts: 1

Kudos [?]: 5 [0], given: 3

Concentration: Operations, General Management
GMAT 1: 650 Q50 V28
Re: If a and b are positive integers, what is the units digit of [#permalink]

### Show Tags

03 Aug 2015, 09:55
Hi Bunuel,

I think it should be A as the question stem states that a & b are positive integers, ruling out the possibility of b being 0.

Kudos [?]: 5 [0], given: 3

Current Student
Joined: 20 Mar 2014
Posts: 2676

Kudos [?]: 1768 [0], given: 794

Concentration: Finance, Strategy
Schools: Kellogg '18 (M)
GMAT 1: 750 Q49 V44
GPA: 3.7
WE: Engineering (Aerospace and Defense)
If a and b are positive integers, what is the units digit of [#permalink]

### Show Tags

03 Aug 2015, 10:14
kakshay108@gmail.com wrote:
Hi Bunuel,

I think it should be A as the question stem states that a & b are positive integers, ruling out the possibility of b being 0.

Not really. Positive integers can also include numbers such as 10, 20, 35 , 77 or even 1000. Having a ,b POSITIVE INTEGERS only means that the selected integers are >0 NOT that their unit's digit is 0 (this may or may not be true as shown below).

Per statement 1, b = 1.25 a

This statement can not be sufficient as you do not know about a.

Take 2 cases:

a= 4, b = 5, units digit = 5

a =16, b = 20, unit's digit = 0 . Hence you get 2 different answers. Thus this statement is not sufficient.

Kudos [?]: 1768 [0], given: 794

Manager
Joined: 24 Nov 2013
Posts: 60

Kudos [?]: 19 [0], given: 115

Re: If a and b are positive integers, what is the units digit of [#permalink]

### Show Tags

17 Sep 2015, 20:50
kakshay108@gmail.com wrote:
Hi Bunuel,

I think it should be A as the question stem states that a & b are positive integers, ruling out the possibility of b being 0.

Bunuel has mentioned that "the units digit of b could be 0"...he is not saying b is 0..Hope this clears your doubt.

Kudos [?]: 19 [0], given: 115

Board of Directors
Joined: 17 Jul 2014
Posts: 2672

Kudos [?]: 431 [1], given: 200

Location: United States (IL)
Concentration: Finance, Economics
GMAT 1: 650 Q49 V30
GPA: 3.92
WE: General Management (Transportation)
Re: If a and b are positive integers, what is the units digit of [#permalink]

### Show Tags

14 Apr 2016, 18:24
1
KUDOS
honchos wrote:
If a and b are positive integers, what is the units digit of b ?

(1) b is 25% greater than a.

(2) If b is decreased by 50%, the result is not an integer.

1. b=5a/4
so a must be a multiple of 4, and b a multiple of 5.
a=4, b=5. a=8, b=10, 2 options, not sufficient.

2. b/2 = non-integer. so b is odd.

1+2. b is odd, and b is a multiple of 5.
5, 15, 25, 35, 45, etc. so always b has units digit 5.

Kudos [?]: 431 [1], given: 200

Director
Joined: 13 Mar 2017
Posts: 552

Kudos [?]: 134 [0], given: 64

Location: India
Concentration: General Management, Entrepreneurship
GPA: 3.8
WE: Engineering (Energy and Utilities)
Re: If a and b are positive integers, what is the units digit of [#permalink]

### Show Tags

05 Oct 2017, 22:35
honchos wrote:
If a and b are positive integers, what is the units digit of b ?

(1) b is 25% greater than a.

(2) If b is decreased by 50%, the result is not an integer.

Given : positive integers a and b
DS: units digit of b?

Statement 1 : b = 1.25 a = (5/4)a
So a is multiple of 4 and b is a multiple of 5
a= 4, b =5
a=8, b=10
a=12, b=15
a=16, b= 20

So, unit's digit of b is either 0 or 5
NOT SUFFICIENT

Statement 2 : Lets say the resultant value is c. So c = 0.5b and c is not an integer.
So, c must be an odd integer. Unit's digit can be 1,3,5,7,9
NOT SUFFICIENT

Combined : Unit's digit = 5
SUFFICIENT
_________________

MBA Social Network : WebMaggu

Appreciate by Clicking +1 Kudos ( Lets be more generous friends.)

Kudos [?]: 134 [0], given: 64

Re: If a and b are positive integers, what is the units digit of   [#permalink] 05 Oct 2017, 22:35
Display posts from previous: Sort by