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

 It is currently 03 Aug 2015, 20:26

### 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

# If Sally can paint a house in 4 hours, and John can paint

Author Message
TAGS:
Intern
Joined: 06 Sep 2012
Posts: 4
Location: United States
Followers: 0

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

If Sally can paint a house in 4 hours, and John can paint [#permalink]  02 Nov 2012, 09:46
00:00

Difficulty:

5% (low)

Question Stats:

99% (01:33) correct 1% (00:00) wrong based on 69 sessions
If Sally can paint a house in 4 hours, and John can paint the same house in 6 hour, how long will it take for both of them to paint the house together?

A. 2 hours and 24 minutes
B. 3 hours and 12 minutes
C. 3 hours and 44 minutes
D. 4 hours and 10 minutes
E. 4 hours and 33 minutes
[Reveal] Spoiler: OA

Last edited by Bunuel on 02 Nov 2012, 13:06, edited 1 time in total.
Renamed the topic and edited the question.
Intern
Joined: 05 Sep 2012
Posts: 1
Followers: 0

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

Re: need some help [#permalink]  02 Nov 2012, 10:16
Hello...

Sally can paint a house in 4 hours; Which means in 1 hour she can paint 1/4th of the house.
John can paint the same house in 6 hours. Which means in 1 hour she can paint 1/6th of the house.

Together in 1 hour they can paint: - 1/4 + 1/6 = 5/12th of the house.

Total Hours for painting the house together will be 12/5 = 2.4 Hours.

Intern
Joined: 06 Sep 2012
Posts: 4
Location: United States
Followers: 0

Kudos [?]: 6 [1] , given: 0

Re: need some help [#permalink]  02 Nov 2012, 10:25
1
KUDOS
shrinivas280390 wrote:
Hello...

Sally can paint a house in 4 hours; Which means in 1 hour she can paint 1/4th of the house.
John can paint the same house in 6 hours. Which means in 1 hour she can paint 1/6th of the house.

Together in 1 hour they can paint: - 1/4 + 1/6 = 5/12th of the house.

Total Hours for painting the house together will be 12/5 = 2.4 Hours.

Thanks a lot I really made a stupid mistake :/
Manager
Joined: 25 Jun 2012
Posts: 65
Followers: 0

Kudos [?]: 22 [0], given: 21

Re: need some help [#permalink]  02 Nov 2012, 12:11
MariaF wrote:
shrinivas280390 wrote:
Hello...

Sally can paint a house in 4 hours; Which means in 1 hour she can paint 1/4th of the house.
John can paint the same house in 6 hours. Which means in 1 hour she can paint 1/6th of the house.

Together in 1 hour they can paint: - 1/4 + 1/6 = 5/12th of the house.

Total Hours for painting the house together will be 12/5 = 2.4 Hours.

Thanks a lot I really made a stupid mistake :/

It'd be interesting how to use elimination techniques solving this problem?
Manager
Joined: 31 Oct 2012
Posts: 61
Schools: Mays '16, Simon '16
GMAT 1: Q V
GMAT 2: Q V
Followers: 0

Kudos [?]: 5 [0], given: 51

Re: need some help [#permalink]  02 Nov 2012, 12:17
MariaF wrote:
Guys, help me please to solve this easy problem. I think I just make a stupid mistake
If Sally can paint a house in 4 hours, and John can paint the same house in 6 hour, how long will it take for both of them to paint the house together?

A. 2 hours and 24 minutes
B. 3 hours and 12 minutes
C. 3 hours and 44 minutes
D. 4 hours and 10 minutes
E. 4 hours and 33 minutes

Time taken will be = x*y/x+y = 4*6/4+6 [ A]
Manager
Joined: 25 Jun 2012
Posts: 65
Followers: 0

Kudos [?]: 22 [0], given: 21

Re: need some help [#permalink]  02 Nov 2012, 12:22
RJSPO wrote:
MariaF wrote:
Guys, help me please to solve this easy problem. I think I just make a stupid mistake
If Sally can paint a house in 4 hours, and John can paint the same house in 6 hour, how long will it take for both of them to paint the house together?

A. 2 hours and 24 minutes
B. 3 hours and 12 minutes
C. 3 hours and 44 minutes
D. 4 hours and 10 minutes
E. 4 hours and 33 minutes

Time taken will be = x*y/x+y = 4*6/4+6 [ A]

Nice trick, I have to remember it, x*y/(x+y)
and if it would be three workers is it equal x*y*z/(x+y+z)?
Manager
Joined: 31 Oct 2012
Posts: 61
Schools: Mays '16, Simon '16
GMAT 1: Q V
GMAT 2: Q V
Followers: 0

Kudos [?]: 5 [0], given: 51

Re: need some help [#permalink]  02 Nov 2012, 12:30
RJSPO wrote:
MariaF wrote:
Guys, help me please to solve this easy problem. I think I just make a stupid mistake
If Sally can paint a house in 4 hours, and John can paint the same house in 6 hour, how long will it take for both of them to paint the house together?

A. 2 hours and 24 minutes
B. 3 hours and 12 minutes
C. 3 hours and 44 minutes
D. 4 hours and 10 minutes
E. 4 hours and 33 minutes

Time taken will be = x*y/x+y = 4*6/4+6 [ A]

Nice trick, I have to remember it, x*y/(x+y)
and if it would be three workers is it equal x*y*z/(x+y+z)?

No, for 3 workers it will be quite a complicated formula : x*y*z/xy+yz+zx
Better to use reciprocal formula for other cases
Senior Manager
Joined: 13 Aug 2012
Posts: 464
Concentration: Marketing, Finance
GMAT 1: Q V0
GPA: 3.23
Followers: 18

Kudos [?]: 287 [0], given: 11

Re: If Sally can paint a house in 4 hours, and John can paint [#permalink]  14 Nov 2012, 03:13
$$\frac{1}{4}+\frac{1}{6}=\frac{10}{24}=\frac{5}{12}$$

$$Rt=W -> \frac{5houses}{12hrs}xt=1$$
$$t=\frac{12}{5}=2\frac{2}{5}hours=2 hours and 24 minutes$$

_________________

Impossible is nothing to God.

Re: If Sally can paint a house in 4 hours, and John can paint   [#permalink] 14 Nov 2012, 03:13
Similar topics Replies Last post
Similar
Topics:
4 When Mary paints a house, it takes her 4 hours. When Lisa joins Mary, 7 24 Feb 2015, 06:45
6 Bruce and Anne can clean their house in 4 hours working toge 10 05 May 2013, 20:49
29 Tom, working alone, can paint a room in 6 hours. Peter and 6 27 Jan 2012, 12:19
8 Tom, working alone, can paint a room in 6 hours. Peter and 13 11 Aug 2011, 07:40
22 Lindsay can paint 1/x of a certain room in one hour 21 08 Aug 2010, 12:46
Display posts from previous: Sort by