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

 It is currently 23 Jul 2018, 03:07

### 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

# If a and b are positive integers, is 3a^2*b divisible by 60?

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

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 47206
If a and b are positive integers, is 3a^2*b divisible by 60?  [#permalink]

### Show Tags

20 Dec 2015, 06:00
00:00

Difficulty:

(N/A)

Question Stats:

68% (01:04) correct 32% (01:14) wrong based on 211 sessions

### HideShow timer Statistics

If a and b are positive integers, is 3a^2*b divisible by 60?

(1) a is divisible by 10.

(2) b is divisible by 18.

_________________
Director
Joined: 10 Mar 2013
Posts: 562
Location: Germany
Concentration: Finance, Entrepreneurship
GMAT 1: 580 Q46 V24
GPA: 3.88
WE: Information Technology (Consulting)
Re: If a and b are positive integers, is 3a^2*b divisible by 60?  [#permalink]

### Show Tags

20 Dec 2015, 06:25
1
Bunuel wrote:
If a and b are positive integers, is 3a^2*b divisible by 60?

(1) a is divisible by 10.

(2) b is divisible by 18.

Question: $$\frac{3b*a^2}{60}$$
(1) $$\frac{3b*(10k)^2}{60}$$ = $$\frac{b*(10k)^2}{20}$$ a is a multiple of 10 and >0 means even if it's only equal to 10 it's divisible by 20 in the last expression. Sufficient
(2) Clearly not sufficient
Answer A
_________________

When you’re up, your friends know who you are. When you’re down, you know who your friends are.

Share some Kudos, if my posts help you. Thank you !

800Score ONLY QUANT CAT1 51, CAT2 50, CAT3 50
GMAT PREP 670
MGMAT CAT 630
KAPLAN CAT 660

Intern
Joined: 08 Nov 2015
Posts: 34
Schools: Pepperdine '19
Re: If a and b are positive integers, is 3a^2*b divisible by 60?  [#permalink]

### Show Tags

30 Jan 2016, 14:53
1
Some people may choose c because they forget to take into account that the question stem has a^2 in it.
So, if a is divisible by 10 = 5*2.
a^2 will have at least two 5s and two 2s.

Thats what the question stem is indirectly asking. Does a^2b have two 2s and one 5.

Thus, 1 is sufficient.

Hence, the answer is A.
BSchool Forum Moderator
Joined: 12 Aug 2015
Posts: 2645
GRE 1: Q169 V154
Re: If a and b are positive integers, is 3a^2*b divisible by 60?  [#permalink]

### Show Tags

16 Mar 2016, 05:32
For a moment i was about to mark C
then realised that 10 *10 which is the least value of A^2 will be divisible by 20
hence choose A
nice question
_________________

MBA Financing:- INDIAN PUBLIC BANKS vs PRODIGY FINANCE!

Getting into HOLLYWOOD with an MBA!

The MOST AFFORDABLE MBA programs!

STONECOLD's BRUTAL Mock Tests for GMAT-Quant(700+)

AVERAGE GRE Scores At The Top Business Schools!

Manager
Joined: 27 Dec 2016
Posts: 231
Concentration: Marketing, Social Entrepreneurship
GPA: 3.65
WE: Marketing (Education)
Re: If a and b are positive integers, is 3*a^2*b  [#permalink]

### Show Tags

05 Sep 2017, 07:59
pushkarajnjadhav wrote:
If a and b are positive integers, is 3*a^2*b divisible by 60?

1) a is divisible by 10.
2) b is divisible by 18.

Kudos if it helps.

Is $$3a^2b$$ divisible by 60?
- We can change 60 into $$2^2*3*5$$.
- Because we already have 3 in the numerator, so our job is to make sure whether a or b has $$2^2$$ and 5 as its factor.

#1
- a divisible by 10 or $$2^5$$. Since our numerator change a into $$a^2$$, so we MUST HAVE $$2^2*5^2$$ in our numerator.
- Whatever value of b, $$3a^2b$$ divisible by 60.
SUFFICIENT.

#2
- b divisible by 18 or $$2*3^2$$, Since we still need to have 5 as factor, we do not know whether a have this factor.
- Divisibility of $$3a^2b$$ by 60 depends solely on the a value - which we don't know here.
INSUFFICIENT.

A.
_________________

There's an app for that - Steve Jobs.

Re: If a and b are positive integers, is 3*a^2*b &nbs [#permalink] 05 Sep 2017, 07:59
Display posts from previous: Sort by

# If a and b are positive integers, is 3a^2*b divisible by 60?

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

# Events & Promotions

 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®.