It is currently 12 Dec 2017, 15:54

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

There is a total of 1,800 pages that needs to be typed. If it takes 90

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

Hide Tags

Expert Post
1 KUDOS received
Math Revolution GMAT Instructor
User avatar
P
Joined: 16 Aug 2015
Posts: 4460

Kudos [?]: 3141 [1], given: 0

GPA: 3.82
Premium Member
There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink]

Show Tags

New post 27 Jul 2017, 16:58
1
This post received
KUDOS
Expert's post
3
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

81% (01:22) correct 19% (01:12) wrong based on 85 sessions

HideShow timer Statistics

There is a total of 1,800 pages that needs to be typed. If it takes 90 minutes when a types alone, 45 minutes when b types alone, and 30 minutes when c types alone. How many minutes does it take if 3 of them work together?

A. 10min
B. 12min
C. 15min
D. 18min
E. 20min
[Reveal] Spoiler: OA

_________________

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.
Find a 10% off coupon code for GMAT Club members.
“Receive 5 Math Questions & Solutions Daily”
Unlimited Access to over 120 free video lessons - try it yourself
See our Youtube demo

Kudos [?]: 3141 [1], given: 0

1 KUDOS received
Director
Director
User avatar
P
Joined: 04 Dec 2015
Posts: 696

Kudos [?]: 334 [1], given: 261

Location: India
Concentration: Technology, Strategy
Schools: ISB '19, IIMA , IIMB, XLRI
WE: Information Technology (Consulting)
GMAT ToolKit User CAT Tests
There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink]

Show Tags

New post 27 Jul 2017, 18:05
1
This post received
KUDOS
MathRevolution wrote:
There is a total of 1,800 pages that needs to be typed. If it takes 90 minutes when a types alone, 45 minutes when b types alone, and 30 minutes when c types alone. How many minutes does it take if 3 of them work together?

A. 10min
B. 12min
C. 15min
D. 18min
E. 20min


It takes \(90\) minutes when "\(a\)" types alone to complete the work.

Rate of work of "\(a\)" \(= \frac{1}{90}\)

It takes \(45\) minutes when "\(b\)" types alone to complete the work.

Rate of work of "\(b\)" \(= \frac{1}{45}\)

It takes \(30\) minutes when "\(c\)" types alone to complete the work.

Rate of work of "\(c\)" \(= \frac{1}{30}\)

Rate of work of "\(a\)\(,\)\(b\) and \(c\)" combined is;

\(\frac{1}{90} + \frac{1}{45} + \frac{1}{30}\) \(=>\) \(\frac{1 + 2 + 3}{90} = \frac{6}{90} = \frac{1}{15}\)

Therefore time taken to complete the job when \(3\) of them work together \(= \frac{1}{(1/15)} = 15\) mins.

Answer (C)...


_________________
Please Press "+1 Kudos" to appreciate. :)

Kudos [?]: 334 [1], given: 261

VP
VP
avatar
P
Joined: 22 May 2016
Posts: 1117

Kudos [?]: 397 [0], given: 640

There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink]

Show Tags

New post 28 Jul 2017, 07:56
MathRevolution wrote:
There is a total of 1,800 pages that needs to be typed. If it takes 90 minutes when a types alone, 45 minutes when b types alone, and 30 minutes when c types alone. How many minutes does it take if 3 of them work together?

A. 10min
B. 12min
C. 15min
D. 18min
E. 20min

Another way: calculate rates using 1800 as \(Work\), then divide by time \(t\) = number of minutes it takes each person to complete all 1800 pages.

\(r= W/t\)

a = 1800 p/90 mins is \((\frac{20p}{1 min})\)

b = 1800 p/45 min is \((\frac{40p}{1 min})\)

c = 1800 p/30 min is \((\frac{60p}{1 min})\)

In one minute, the three together can type 20 + 40 + 60 = 120 pages, i.e., \((\frac{120p}{1 min})\)

1800 pages/120 pages in 1 minute = 15 minutes to finish when working together

Answer C

Kudos [?]: 397 [0], given: 640

Manager
Manager
avatar
B
Joined: 02 Nov 2015
Posts: 176

Kudos [?]: 27 [0], given: 121

GMAT 1: 640 Q49 V29
Premium Member CAT Tests
Re: There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink]

Show Tags

New post 28 Jul 2017, 10:16
Total To be typed divided by individual capacity of each.
A can type 1800/90 i.e 20 per minute . Similarly B can type 1800/45 and C can type 1800/30 per minute.
Therefore together they take 1800/(20+40+60)= 1800/120 = 15.
C is answer

Sent from my Lenovo TAB S8-50LC using GMAT Club Forum mobile app

Kudos [?]: 27 [0], given: 121

Expert Post
Math Revolution GMAT Instructor
User avatar
P
Joined: 16 Aug 2015
Posts: 4460

Kudos [?]: 3141 [0], given: 0

GPA: 3.82
Premium Member
Re: There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink]

Show Tags

New post 30 Jul 2017, 17:58
==> For work rate questions, if there is a “together and alone”, you need to solve the question reciprocally. In other words, A: 1,800pg/90mins, B:1,800pg/45mins, C: 1,800pg/30mins, and if you assume A&B&C:1,800pg/t mins, you get (1/90)+(1/45)+(1/30)=(1/t), and from (1+2+3)/90=1/t, you get t=15.

The answer is C.
Answer: C
_________________

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.
Find a 10% off coupon code for GMAT Club members.
“Receive 5 Math Questions & Solutions Daily”
Unlimited Access to over 120 free video lessons - try it yourself
See our Youtube demo

Kudos [?]: 3141 [0], given: 0

Expert Post
Target Test Prep Representative
User avatar
S
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 1793

Kudos [?]: 980 [0], given: 5

Re: There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink]

Show Tags

New post 01 Aug 2017, 16:22
MathRevolution wrote:
There is a total of 1,800 pages that needs to be typed. If it takes 90 minutes when a types alone, 45 minutes when b types alone, and 30 minutes when c types alone. How many minutes does it take if 3 of them work together?

A. 10min
B. 12min
C. 15min
D. 18min
E. 20min


The combined rate of typists a, b, and c is:

1800/90 + 1800/45 + 1800/30 = 20 + 40 + 60 = 120 pages per minute.

Thus, when working together, the typists complete the job in 1800/120 = 15 minutes.

Answer: C
_________________

Jeffery Miller
Head of GMAT Instruction

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Kudos [?]: 980 [0], given: 5

Re: There is a total of 1,800 pages that needs to be typed. If it takes 90   [#permalink] 01 Aug 2017, 16:22
Display posts from previous: Sort by

There is a total of 1,800 pages that needs to be typed. If it takes 90

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


GMAT Club MBA Forum Home| About| Terms and Conditions| 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®.