Last visit was: 05 Jun 2024, 09:43 It is currently 05 Jun 2024, 09:43
Decision Tracker
My Rewards
Unanswered
Active Topics
New posts
New comers' posts
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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

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

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
L
MathRevolution
Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 10148
Own Kudos [?]: 16776 [4]
Given Kudos: 4
GMAT 1: 760 Q51 V42
GPA: 3.82
Send PM
There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink] There is a total of 1,800 pages that needs to be typed. If it takes 90   27 Jul 2017, 17:58
1
Kudos
3
Bookmarks
Expert Reply
00:00
A
B
C
D
E

Difficulty:

5% (low)

Question Stats:

91% (01:35) correct 9% (02:10) wrong based on 127 sessions
Hide Show DIFFICULTY AND 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
ShowHide Answer
Official Answer
C
User avatar
L
sashiim20
Director
Director
Joined: 04 Dec 2015
Posts: 620
Own Kudos [?]: 1600 [1]
Given Kudos: 276
Location: India
Concentration: Technology, Strategy
Schools: ISB '19 IIMB IIMA XLRI HEC Sept19 intake Rotman '21 NUS '21 NTU '20 Trinity MBA '20 Bocconi '21 Smurfit "21
WE:Information Technology (Consulting)
Send PM
GMAT ToolKit User
There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink] There is a total of 1,800 pages that needs to be typed. If it takes 90   27 Jul 2017, 19:05
1
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. :)
User avatar
L
generis
Senior SC Moderator
Joined: 22 May 2016
Posts: 5329
Own Kudos [?]: 35629 [0]
Given Kudos: 9464
Send PM
CAT Tests
There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink] There is a total of 1,800 pages that needs to be typed. If it takes 90   28 Jul 2017, 08:56
Expert Reply
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
User avatar
B
kumarparitosh123
Manager
Manager
Joined: 02 Nov 2015
Posts: 133
Own Kudos [?]: 57 [0]
Given Kudos: 121
GMAT 1: 640 Q49 V29
Send PM
Re: There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink] There is a total of 1,800 pages that needs to be typed. If it takes 90   28 Jul 2017, 11:16
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
User avatar
L
MathRevolution
Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 10148
Own Kudos [?]: 16776 [0]
Given Kudos: 4
GMAT 1: 760 Q51 V42
GPA: 3.82
Send PM
Re: There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink] There is a total of 1,800 pages that needs to be typed. If it takes 90   30 Jul 2017, 18:58
Expert Reply
==> 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
User avatar
P
JeffTargetTestPrep
Target Test Prep Representative
Joined: 04 Mar 2011
Status:Head GMAT Instructor
Affiliations: Target Test Prep
Posts: 3042
Own Kudos [?]: 6421 [0]
Given Kudos: 1646
Send PM
Re: There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink] There is a total of 1,800 pages that needs to be typed. If it takes 90   01 Aug 2017, 17:22
Expert Reply
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
GMAT Club Bot
gmatclubot
Re: There is a total of 1,800 pages that needs to be typed. If it takes 90 [#permalink]
01 Aug 2017, 17:22
Moderator:
Bunuel
Math Expert
93500 posts