Summer is Coming! Join the Game of Timers Competition to Win Epic Prizes. Registration is Open. Game starts Mon July 1st.

It is currently 18 Jul 2019, 02:01

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

A certain hotel has 1,400 single rooms and 420 double rooms. Each room

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

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56261
A certain hotel has 1,400 single rooms and 420 double rooms. Each room  [#permalink]

Show Tags

New post 11 Nov 2015, 00:49
3
3
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

82% (02:35) correct 18% (03:00) wrong based on 233 sessions

HideShow timer Statistics


A certain hotel has 1,400 single rooms and 420 double rooms. Each room is cleaned by one person. If one person can clean a single room every 15 minutes and a double room every 20 minutes, how many cleaning persons are needed to clean all the rooms if each person works for exactly 7 hours?

(A) 65
(B) 70
(C) 80
(D) 90
(E) 265

_________________
Most Helpful Community Reply
Verbal Forum Moderator
User avatar
V
Status: Greatness begins beyond your comfort zone
Joined: 08 Dec 2013
Posts: 2351
Location: India
Concentration: General Management, Strategy
Schools: Kelley '20, ISB '19
GPA: 3.2
WE: Information Technology (Consulting)
GMAT ToolKit User Reviews Badge CAT Tests
Re: A certain hotel has 1,400 single rooms and 420 double rooms. Each room  [#permalink]

Show Tags

New post 11 Nov 2015, 01:13
7
5
Number of single rooms= 1400
Number of double rooms = 420
Time taken by a person to clean a single room = 15 mins = 1/4 hour
Time taken by a person to clean a double room = 20 mins =1/3 hour

Total time to clean 1400 single and 420 double rooms
= 1400*1/4 + 420 * 1/3
= 350 + 140
= 490 hours

Each person works for = 7 hours

Number of persons required = 490/7 = 70

Answer B
_________________
When everything seems to be going against you, remember that the airplane takes off against the wind, not with it. - Henry Ford
The Moment You Think About Giving Up, Think Of The Reason Why You Held On So Long
+1 Kudos if you find this post helpful
General Discussion
Director
Director
User avatar
D
Joined: 05 Mar 2015
Posts: 992
Re: A certain hotel has 1,400 single rooms and 420 double rooms. Each room  [#permalink]

Show Tags

New post 21 Jan 2017, 22:25
1
Bunuel wrote:
A certain hotel has 1,400 single rooms and 420 double rooms. Each room is cleaned by one person. If one person can clean a single room every 15 minutes and a double room every 20 minutes, how many cleaning persons are needed to clean all the rooms if each person works for exactly 7 hours?

(A) 65
(B) 70
(C) 80
(D) 90
(E) 265


for single room, one person can clean 4 rooms in 1 hr.
thus in 7 hrs =7*4=28 rooms
Persons required for 1400 rooms= 1400/28= 50 persons
similarly
for double room, one person can clean 3 rooms in 1 hr.
thus in 7 hrs =7*3=21 rooms
Persons required for 420 rooms= 420/21 =20 persons

thus total no. of persons = persons required for single room + persons required for double rooms
=50 + 20=70

Ans B
Senior SC Moderator
avatar
V
Joined: 22 May 2016
Posts: 3076
Re: A certain hotel has 1,400 single rooms and 420 double rooms. Each room  [#permalink]

Show Tags

New post 03 Feb 2018, 17:41
Bunuel wrote:
A certain hotel has 1,400 single rooms and 420 double rooms. Each room is cleaned by one person. If one person can clean a single room every 15 minutes and a double room every 20 minutes, how many cleaning persons are needed to clean all the rooms if each person works for exactly 7 hours?

(A) 65
(B) 70
(C) 80
(D) 90
(E) 265

Attachment:
cleanersRTW.png
cleanersRTW.png [ 18.36 KiB | Viewed 1650 times ]

1) Use a modified RT = W formula.
Add (# of workers) to LHS:
(# of workers) * rate * time = Work
Manipulate it just as you would RT = W

2) change cleaning rates from minutes to hours
(All units must be the same. Each cleaner works 7 hours.)

Single room cleaning rate in hours:
\(\frac{1room}{15mins}=\frac{4rooms}{60mins}=\frac{4rooms}{1hour}= 4\)

Double room cleaning rate in hours:
\(\frac{1room}{20mins}=\frac{3rooms}{60mins}=\frac{3rooms}{1hour}= 3\)

3) Calculate number of persons needed for each kind of room

Single rooms
\(\frac{W}{r*t}=\) number of cleaning persons needed

\(\frac{1,400}{(4*7)}=\frac{1,400}{28}= 50\) persons needed

Double rooms
\(\frac{W}{r*t}=\) number of cleaning persons needed

\(\frac{420}{(3*7)}=\frac{420}{21}= 20\) persons needed

Total persons needed: (50 + 20) = 70

Answer B
_________________
SC Butler has resumed!
Get two SC questions to practice, whose links you can find by date, here.


Tell me, what is it you plan to do with your one wild and precious life? -- Mary Oliver
EMPOWERgmat Instructor
User avatar
V
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 14567
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: A certain hotel has 1,400 single rooms and 420 double rooms. Each room  [#permalink]

Show Tags

New post 17 Mar 2018, 11:47
Hi All,

This is essentially a rate question. Here's how to solve it:

Single rooms take one person 15 minutes to clean and double rooms take one person 20 minutes to clean.

15 mins. = 1/4 hour
20 mins. = 1/3 hour

With 1400 single rooms x 1/4 hour = 350 hours of total work for 1 person
With 420 double rooms x 1/3 hour = 140 hours of total work for 1 person

For ALL the rooms, we have a total of 350 + 140 = 490 hours of total work for 1 person

To get the work done in 7 hours, we'll need 490/7 = 70 workers

Final Answer:

GMAT assassins aren't born, they're made,
Rich
_________________
760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

*****Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!*****

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/
CEO
CEO
User avatar
V
Joined: 12 Sep 2015
Posts: 3848
Location: Canada
Re: A certain hotel has 1,400 single rooms and 420 double rooms. Each room  [#permalink]

Show Tags

New post 13 Mar 2019, 06:44
Top Contributor
Bunuel wrote:
A certain hotel has 1,400 single rooms and 420 double rooms. Each room is cleaned by one person. If one person can clean a single room every 15 minutes and a double room every 20 minutes, how many cleaning persons are needed to clean all the rooms if each person works for exactly 7 hours?

(A) 65
(B) 70
(C) 80
(D) 90
(E) 265


The hotel has 1,400 single rooms, and one person can clean a single room every 15 minutes
So, one person can clean 4 single rooms in ONE HOUR
In other words, it takes 1 WORKER HOUR to clean 4 single rooms

1400/4 = 350
So, it takes 350 WORKER HOURS to clean 1400 rooms

The hotel has 420 double rooms, and one person can clean a double room every 20 minutes
So, one person can clean 3 double rooms in ONE HOUR
In other words, it takes 1 WORKER HOUR to clean 3 double rooms

420/3 = 140
So, it takes 140 WORKER HOURS to clean 420 double rooms

How many cleaning persons are needed to clean all the rooms if each person works for exactly 7 hours?
350 + 140 = 490
So, 490 WORKER HOURS are required to clean ALL of the room.

490/7 = 70.
So, 70 workers are needed.

Answer: B

Cheers,
Brent
_________________
Test confidently with gmatprepnow.com
Image
Target Test Prep Representative
User avatar
D
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 6923
Location: United States (CA)
Re: A certain hotel has 1,400 single rooms and 420 double rooms. Each room  [#permalink]

Show Tags

New post 15 Mar 2019, 06:02
Bunuel wrote:
A certain hotel has 1,400 single rooms and 420 double rooms. Each room is cleaned by one person. If one person can clean a single room every 15 minutes and a double room every 20 minutes, how many cleaning persons are needed to clean all the rooms if each person works for exactly 7 hours?

(A) 65
(B) 70
(C) 80
(D) 90
(E) 265


It takes 1400 x 1/4 = 350 hours to clean the single rooms and 420 x 1/3 = 140 hours to clean the double rooms, for a total time of 490 hours. We can let n = the number of workers and create the equation:

7n = 490

n = 70

Answer: B
_________________

Scott Woodbury-Stewart

Founder and CEO

Scott@TargetTestPrep.com
TTP - Target Test Prep Logo
122 Reviews

5-star rated online GMAT quant
self study course

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button.

GMAT Club Bot
Re: A certain hotel has 1,400 single rooms and 420 double rooms. Each room   [#permalink] 15 Mar 2019, 06:02
Display posts from previous: Sort by

A certain hotel has 1,400 single rooms and 420 double rooms. Each room

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





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne