Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 06 Oct 2015, 17:02

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Working alone at a constant rate

Author Message
TAGS:
Manager
Joined: 18 Aug 2011
Posts: 60
Followers: 1

Kudos [?]: 19 [0], given: 6

Working alone at a constant rate [#permalink]  26 Aug 2011, 01:10
00:00

Difficulty:

(N/A)

Question Stats:

57% (02:20) correct 43% (02:07) wrong based on 25 sessions
Working alone at a constant rate, Alan can paint a house in a hours. Working alone at a constant rate, Bob can point 1/4 of the same house in b hours. Working together, Alan and Bob can paint 1/3 of the house in c hours. What is the value of b in terms of a and c?

a) (3ac)/(a+c)
b) (4a-12c)/(3ac)
c) (3ac)/(4a-12c)
d) (ac)/(a+2c)
e) (ac)/(a+c)
Director
Joined: 01 Feb 2011
Posts: 759
Followers: 14

Kudos [?]: 77 [0], given: 42

Re: Working alone at a constant rate [#permalink]  26 Aug 2011, 16:38
work time

A 1 a
B 1/4 b

A+B 1/3 c

A's rate = 1/a

B's rate = 1/4b

when they are working together , their combined rate is 1/a + 1/(4b) = (1/3)/c

1/(4b) = 1/(3c) - 1/a

=> b = 3ac /(4a-12c)

Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2026
Followers: 145

Kudos [?]: 1258 [0], given: 376

Re: Working alone at a constant rate [#permalink]  27 Aug 2011, 06:42
Berbatov wrote:
Working alone at a constant rate, Alan can paint a house in a hours. Working alone at a constant rate, Bob can point 1/4 of the same house in b hours. Working together, Alan and Bob can paint 1/3 of the house in c hours. What is the value of b in terms of a and c?

a) (3ac)/(a+c)
b) (4a-12c)/(3ac)
c) (3ac)/(4a-12c)
d) (ac)/(a+2c)
e) (ac)/(a+c)

Alan's rate= 1/a
Bob's rate= 1/(4b)
Combined rate= 1/(3c)

$$\frac{1}{a}+\frac{1}{4b}=\frac{1}{3c}$$

Upon solving:
$$b=\frac{3ac}{4a-12c}$$

Ans: "C"
_________________
Intern
Joined: 31 May 2010
Posts: 38
Followers: 0

Kudos [?]: 2 [0], given: 2

Re: Working alone at a constant rate [#permalink]  27 Aug 2011, 11:07
C only
Manager
Joined: 25 May 2011
Posts: 158
Followers: 2

Kudos [?]: 47 [1] , given: 71

Re: Working alone at a constant rate [#permalink]  30 Oct 2011, 09:19
1
KUDOS
Alan's time to complete the task: a
Bob's time to complete the task: 4b
Together: 3c

$$\frac{1}{a}+\frac{1}{4b}=\frac{1}{3c}$$

$$b=\frac{3ac}{4a-12c}$$

Re: Working alone at a constant rate   [#permalink] 30 Oct 2011, 09:19
Similar topics Replies Last post
Similar
Topics:
1 While working alone at their respective constant rates, 5 09 Feb 2013, 13:37
5 Working at their respective constant rates, Paul, Abdul and Adam alone 7 23 Sep 2011, 00:35
6 While working alone at their constant rates computer X can process 240 11 29 Mar 2011, 03:36
22 Working alone at its own constant rate, a machine seals k 16 17 Nov 2010, 07:35
11 Working alone at its own constant rate, a machine seals k 17 13 Oct 2009, 11:13
Display posts from previous: Sort by