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

It is currently 25 Apr 2019, 07:18

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

An alarm of a certain clock rings every 20 minutes. If the clock's ala

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

Hide Tags

 
Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 7251
GMAT 1: 760 Q51 V42
GPA: 3.82
An alarm of a certain clock rings every 20 minutes. If the clock's ala  [#permalink]

Show Tags

New post Updated on: 18 Aug 2017, 19:54
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

85% (01:20) correct 15% (01:41) wrong based on 121 sessions

HideShow timer Statistics

An alarm of a certain clock rings every 20 minutes. If the clock's alarm first rings at 15:20, when will the 12th alarm of the clock ring?

A. 17:30
B. 18:00
C. 18:30
D. 19:00
E. 19:30

_________________
MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $149 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Originally posted by MathRevolution on 16 Aug 2017, 02:43.
Last edited by MathRevolution on 18 Aug 2017, 19:54, edited 2 times in total.
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 54543
Re: An alarm of a certain clock rings every 20 minutes. If the clock's ala  [#permalink]

Show Tags

New post 16 Aug 2017, 02:46
Intern
Intern
avatar
B
Joined: 22 Apr 2015
Posts: 25
WE: Business Development (Internet and New Media)
Reviews Badge
Re: An alarm of a certain clock rings every 20 minutes. If the clock's ala  [#permalink]

Show Tags

New post 16 Aug 2017, 03:57
2
the alarm rings every 20 mins. => d= 20 min= \(\frac{1}{3}\) hr
1st ring at 15:20. => a= 15:20= (15+\(\frac{1}{3}\)) hr=\(\frac{46}{3}\) hr
12th ring= t12= a+(12-1)d= a+11d= \(\frac{46}{3}\)+\(\frac{1}{3}\)= \(\frac{57}{3}\) hr= 19 hr= 19:00

Ans- D
Senior Manager
Senior Manager
User avatar
P
Joined: 29 Jun 2017
Posts: 454
GPA: 4
WE: Engineering (Transportation)
GMAT ToolKit User Reviews Badge
Re: An alarm of a certain clock rings every 20 minutes. If the clock's ala  [#permalink]

Show Tags

New post 16 Aug 2017, 04:07
@Buenel

My Answer is D here
just to prove D is correct and official answer is may be wrong.
first ring - 15:20
2nd 15:40
3rd 16:00
4th. 16:20
5th. 16:40
6. 17:00
7. 17:20
8. 17:40
9. 18:00
10. 18:20
11. 18:40
12th ring 19:00
Kudos for correct answer.
Also would like to mention i correctly answered https://gmatclub.com/forum/an-alarm-of- ... 44589.html question as well.
_________________
Give Kudos for correct answer and/or if you like the solution.
Senior SC Moderator
avatar
V
Joined: 22 May 2016
Posts: 2653
Re: An alarm of a certain clock rings every 20 minutes. If the clock's ala  [#permalink]

Show Tags

New post 16 Aug 2017, 15:23
MathRevolution wrote:
An alarm of a certain clock rings every 20 minutes. If the clock's alarm first rings at 15:20, when will the 12th alarm of the clock ring?

A. 17:30
B. 18:00
C. 18:30
D. 19:00
E. 19:30

MathRevolution , or Bunuel , or some moderator, would you please check the answer choices? I got D, and so did others who posted here.

I ran it twice more, using different methods. Still got Answer D.
_________________
Listen, are you breathing just a little, and calling it a life?
-- Mary Oliver



For practice SC questions with official explanations that were posted and moderated by the SC Team,
go to SC Butler here: https://gmatclub.com/forum/project-sc-butler-get-2-sc-questions-everyday-281043.html
SVP
SVP
User avatar
V
Joined: 26 Mar 2013
Posts: 2138
Reviews Badge CAT Tests
Re: An alarm of a certain clock rings every 20 minutes. If the clock's ala  [#permalink]

Show Tags

New post 16 Aug 2017, 16:05
MathRevolution wrote:
An alarm of a certain clock rings every 20 minutes. If the clock's alarm first rings at 15:20, when will the 12th alarm of the clock ring?

A. 17:30
B. 18:00
C. 18:30
D. 19:00
E. 19:30



the 12th ring = 15:20 + 1/3 * 11 = 15:20 + 3:40 = 19:00

Answer: D
Intern
Intern
avatar
Joined: 18 Aug 2017
Posts: 2
Re: An alarm of a certain clock rings every 20 minutes. If the clock's ala  [#permalink]

Show Tags

New post 18 Aug 2017, 02:44
First alarm rings at 1520
Thus 12 alarm will ring in 11*20 =220 min
Thus 12th tym alarm will ring at 1520 + 3 hrs 40 min
Hence ans 1900 hrs
Ans D


Sent from my iPhone using GMAT Club Forum mobile app
Math Expert
User avatar
V
Joined: 02 Aug 2009
Posts: 7589
Re: An alarm of a certain clock rings every 20 minutes. If the clock's ala  [#permalink]

Show Tags

New post 18 Aug 2017, 03:36
MathRevolution wrote:
An alarm of a certain clock rings every 20 minutes. If the clock's alarm first rings at 15:20, when will the 12th alarm of the clock ring?

A. 17:30
B. 18:00
C. 18:30
D. 19:00
E. 19:30



Hi..
If a clock rings at interval of 20 minutes and starts at 1520...
Ans has to be at _ _ 20, _ _ 40 or _ _ 60, can't be at _ _ 30

So answer given is clearly wrong ..

Now ans is 11*20+ 1520h..
11*20/60= 11/3= 3+2/3.. so 3 hours and 60*2/3=40 min.
So 15:20 + 3 hour and 30 mins=1900

D

Editing the OA
_________________
Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 7251
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: An alarm of a certain clock rings every 20 minutes. If the clock's ala  [#permalink]

Show Tags

New post 20 Aug 2017, 18:25
=>The third alarm rings at 16:00, the sixth alarm rings at 17:00. Thus every third alarm rings every hour on the hour. The 12th alarm rings at 19:00.

Ans: D
_________________
MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $149 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"
GMAT Club Bot
Re: An alarm of a certain clock rings every 20 minutes. If the clock's ala   [#permalink] 20 Aug 2017, 18:25
Display posts from previous: Sort by

An alarm of a certain clock rings every 20 minutes. If the clock's ala

  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®.