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

It is currently 22 Oct 2018, 00:49

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

If a and b are single digits from 0 to 9, inclusive, what is the value

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

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50036
If a and b are single digits from 0 to 9, inclusive, what is the value  [#permalink]

Show Tags

New post 28 Jul 2017, 04:01
1
1
00:00
A
B
C
D
E

Difficulty:

  85% (hard)

Question Stats:

59% (02:28) correct 41% (02:39) wrong based on 72 sessions

HideShow timer Statistics

If a and b are single digits from 0 to 9, inclusive, what is the value of (a + b)?

(1) The number 25a7b is divisible by 36.
(2) The number a1b is divisible by 4.

_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

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?
Extra-hard Quant Tests with Brilliant Analytics

Director
Director
User avatar
P
Joined: 18 Aug 2016
Posts: 625
Concentration: Strategy, Technology
GMAT 1: 630 Q47 V29
GMAT 2: 740 Q51 V38
GMAT ToolKit User Premium Member Reviews Badge CAT Tests
Re: If a and b are single digits from 0 to 9, inclusive, what is the value  [#permalink]

Show Tags

New post 28 Jul 2017, 04:42
1
Bunuel wrote:
If a and b are single digits from 0 to 9, inclusive, what is the value of (a + b)?

(1) The number 25a7b is divisible by 36.
(2) The number a1b is divisible by 4.


(1)
36*2 = 72
only when b = 2 we can get 7 in the tenth digit
36*702 = 25272
36*712 = 25632 nope
36*722 = 25992 nope
36*692 = 24912 nope
hence a+b = 4

Sufficient

(2) a1b is divisible by 4
b can take 2, 6
a can take 1-9
Not sufficient

A
_________________

We must try to achieve the best within us


Thanks
Luckisnoexcuse

Director
Director
avatar
S
Joined: 21 Mar 2016
Posts: 530
Reviews Badge
Re: If a and b are single digits from 0 to 9, inclusive, what is the value  [#permalink]

Show Tags

New post 28 Jul 2017, 08:46
1
mynamegoeson wrote:
Bunuel wrote:
If a and b are single digits from 0 to 9, inclusive, what is the value of (a + b)?

(1) The number 25a7b is divisible by 36.
(2) The number a1b is divisible by 4.


(1)
36*2 = 72
only when b = 2 we can get 7 in the tenth digit
36*702 = 25272
36*712 = 25632 nope
36*722 = 25992 nope
36*692 = 24912 nope
hence a+b = 4

Sufficient

(2) a1b is divisible by 4
b can take 2, 6
a can take 1-9
Not sufficient

A



luks like E to me....
here are my 2 cents....
if the number is divisible by 36,,it shud be divisible by both 9 and 4
for a number to b divisible by 9,, the sum if digits shud be divisible by 9
for a nummber to b divisible by 4 the last two digits shud be divisible by 4


stat 1: 25776,, a+b = 13
25272 ,,a+b = 4
not suff

stat 2: b can be 2 or 6

both combined two diff ans,,
ans E
Manager
Manager
User avatar
B
Joined: 03 May 2017
Posts: 99
GMAT ToolKit User
If a and b are single digits from 0 to 9, inclusive, what is the value  [#permalink]

Show Tags

New post Updated on: 28 Jul 2017, 09:40
Bunuel wrote:
If a and b are single digits from 0 to 9, inclusive, what is the value of (a + b)?

(1) The number 25a7b is divisible by 36.
(2) The number a1b is divisible by 4.


IMO, it helps to start from statement 2 as it's much simpler and may give hints to evaluate statement 1
Statement 2 is insufficient using the divisibility rule by 4 i.e b is either 2 or 6 and a could be any number.

Evaluating statement 1:
From statement 2 we know that b is either 2 or 6 since it's divisible by 25a7b is divisible by 36,

Now combining the divisibility by 4 and 9 to find divisibility by 36, b is inconclusive as 72 and 76 are divisible by 4
Also by extension, a has dual values (2 and 7) that make 2+a+5+7+2 = 18 or 2+a+5+7+6 = 27 divisible by 9

Thus, statement 1 is also insufficient and the answer is E.[/b]

Originally posted by rulingbear on 28 Jul 2017, 09:05.
Last edited by rulingbear on 28 Jul 2017, 09:40, edited 2 times in total.
Director
Director
avatar
S
Joined: 21 Mar 2016
Posts: 530
Reviews Badge
Re: If a and b are single digits from 0 to 9, inclusive, what is the value  [#permalink]

Show Tags

New post 28 Jul 2017, 09:10
1
rulingbear wrote:
Bunuel wrote:
If a and b are single digits from 0 to 9, inclusive, what is the value of (a + b)?

(1) The number 25a7b is divisible by 36.
(2) The number a1b is divisible by 4.


IMO, it helps to start from statement 2 as it's much simpler and may give hints to evaluate statement 1
Statement 2 is insufficient using the divisibility rule by 4 i.e b is either 2 or 6 and a could be any number.

From statement 2 we know that b is either 2 or 6 since it's divisible by 25a7b is divisible by 36, b is clearly 2, i.e last 2 digits cannot be 76.
Now we need to find a, here by approximation the first # of the quotient is 7, i.e 36(8-1) = 288-36= 252
Hence a is clearly 2, as any other number would spill over and would make 25a7b indivisible by 36.
Thus, 1 is sufficient and the answer is A.



in the number 25776, the last two digits are 76,,, and the number is very much divisible by 36...
Manager
Manager
User avatar
B
Joined: 03 May 2017
Posts: 99
GMAT ToolKit User
Re: If a and b are single digits from 0 to 9, inclusive, what is the value  [#permalink]

Show Tags

New post 28 Jul 2017, 09:15
mohshu wrote:
rulingbear wrote:
Bunuel wrote:
If a and b are single digits from 0 to 9, inclusive, what is the value of (a + b)?

(1) The number 25a7b is divisible by 36.
(2) The number a1b is divisible by 4.


IMO, it helps to start from statement 2 as it's much simpler and may give hints to evaluate statement 1
Statement 2 is insufficient using the divisibility rule by 4 i.e b is either 2 or 6 and a could be any number.

From statement 2 we know that b is either 2 or 6 since it's divisible by 25a7b is divisible by 36, b is clearly 2, i.e last 2 digits cannot be 76.
Now we need to find a, here by approximation the first # of the quotient is 7, i.e 36(8-1) = 288-36= 252
Hence a is clearly 2, as any other number would spill over and would make 25a7b indivisible by 36.
Thus, 1 is sufficient and the answer is A.



in the number 25776, the last two digits are 76,,, and the number is very much divisible by 36...


Hi Monshu,

You are clearly right, missed that.
Intern
Intern
User avatar
B
Joined: 06 Feb 2016
Posts: 48
Location: Poland
Concentration: Finance, Accounting
GMAT 1: 730 Q49 V41
GPA: 3.5
Re: If a and b are single digits from 0 to 9, inclusive, what is the value  [#permalink]

Show Tags

New post 28 Jul 2017, 11:53
The answer should be E.
Both statements combined you will have two cases:
b=2
and
b=6
Intern
Intern
avatar
B
Joined: 21 Jun 2017
Posts: 10
GMAT 1: 750 Q50 V41
Re: If a and b are single digits from 0 to 9, inclusive, what is the value  [#permalink]

Show Tags

New post 29 Jul 2017, 12:45
mynamegoeson wrote:
Bunuel wrote:
If a and b are single digits from 0 to 9, inclusive, what is the value of (a + b)?

(1) The number 25a7b is divisible by 36.
(2) The number a1b is divisible by 4.


(1)
36*2 = 72
only when b = 2 we can get 7 in the tenth digit
36*702 = 25272
36*712 = 25632 nope
36*722 = 25992 nope
36*692 = 24912 nope
hence a+b = 4

Sufficient

(2) a1b is divisible by 4
b can take 2, 6
a can take 1-9
Not sufficient

A


You are forgetting 25776
(1) Divisible by 36 means divisible by 4 and 9.
divisible by 4 means 7b divisible by 4 --> b=2 or 6
divisible by 9 means 2+5+7+a+b divisible by 9 but b can only take 2 or 6
with b=2 --> 16+a divisible by 9 --> a=2
with b=6 --> 20+a divisible by 9 --> a=7
(2) same info

E
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 8515
Premium Member
Re: If a and b are single digits from 0 to 9, inclusive, what is the value  [#permalink]

Show Tags

New post 20 Sep 2018, 05:14
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

GMAT Club Bot
Re: If a and b are single digits from 0 to 9, inclusive, what is the value &nbs [#permalink] 20 Sep 2018, 05:14
Display posts from previous: Sort by

If a and b are single digits from 0 to 9, inclusive, what is the value

  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®.