GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 21 Oct 2018, 23:11

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

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

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

Hide Tags

Intern
Intern
avatar
Joined: 06 Sep 2012
Posts: 4
Location: United States
Concentration: Marketing, International Business
If Sally can paint a house in 4 hours, and John can paint  [#permalink]

Show Tags

New post Updated on: 02 Nov 2012, 14:06
6
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

94% (01:05) correct 6% (01:44) wrong based on 346 sessions

HideShow timer Statistics

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

Originally posted by MariaF on 02 Nov 2012, 10:46.
Last edited by Bunuel on 02 Nov 2012, 14:06, edited 1 time in total.
Renamed the topic and edited the question.
Intern
Intern
avatar
Joined: 05 Sep 2012
Posts: 1
Re: need some help  [#permalink]

Show Tags

New post 02 Nov 2012, 11:16
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.

Hence Answer A
Intern
Intern
avatar
Joined: 06 Sep 2012
Posts: 4
Location: United States
Concentration: Marketing, International Business
Re: need some help  [#permalink]

Show Tags

New post 02 Nov 2012, 11:25
1
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.

Hence Answer A


Thanks a lot :) I really made a stupid mistake :/
Manager
Manager
avatar
Joined: 25 Jun 2012
Posts: 64
Re: need some help  [#permalink]

Show Tags

New post 02 Nov 2012, 13:11
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.

Hence Answer A


Thanks a lot :) I really made a stupid mistake :/


It'd be interesting how to use elimination techniques solving this problem? :?:
Manager
Manager
avatar
Joined: 31 Oct 2012
Posts: 59
Schools: Mays '16, Simon '16
Re: need some help  [#permalink]

Show Tags

New post 02 Nov 2012, 13:17
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
Manager
avatar
Joined: 25 Jun 2012
Posts: 64
Re: need some help  [#permalink]

Show Tags

New post 02 Nov 2012, 13:22
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
Manager
avatar
Joined: 31 Oct 2012
Posts: 59
Schools: Mays '16, Simon '16
Re: need some help  [#permalink]

Show Tags

New post 02 Nov 2012, 13:30
actleader wrote:
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
Senior Manager
User avatar
Joined: 13 Aug 2012
Posts: 431
Concentration: Marketing, Finance
GPA: 3.23
GMAT ToolKit User
Re: If Sally can paint a house in 4 hours, and John can paint  [#permalink]

Show Tags

New post 14 Nov 2012, 04:13
\(\frac{1}{4}+\frac{1}{6}=\frac{10}{24}=\frac{5}{12}\)

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

Answer: B
_________________

Impossible is nothing to God.

Manager
Manager
User avatar
S
Joined: 22 Nov 2016
Posts: 214
Location: United States
Concentration: Leadership, Strategy
GPA: 3.4
Reviews Badge
Re: If Sally can paint a house in 4 hours, and John can paint  [#permalink]

Show Tags

New post 26 Jun 2017, 16:48
\(W=\frac{AB}{A+B}\) where A and B are rates and W is the work done.

A=4; B=6
\(W=\frac{24}{10}\)

To convert to minutes \(= \frac{24}{10}*60 = 144\) minutes
120+24 minutes , i.e 2 hours and 24 mins
Answer is A
_________________

Kudosity killed the cat but your kudos can save it.

CEO
CEO
User avatar
D
Joined: 12 Sep 2015
Posts: 3024
Location: Canada
Re: If Sally can paint a house in 4 hours, and John can paint  [#permalink]

Show Tags

New post 26 Jun 2017, 18:18
Top Contributor
1
MariaF wrote:
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


We can solve this question quickly by using a little number sense.

Sally can paint a house in 4 hours
So, if there were TWO Sallys, they'd be able to paint the house in HALF the time.
In other words, TWO Sallys could paint the house in 2 hours

John can paint the same house in 6 hours
So, if there were TWO Johns, they'd be able to paint the house in HALF the time.
In other words, TWO Johns could paint the house in 3 hours

So, the time it takes Sally and John to paint the house will be BETWEEN 2 hours and 3 hours

This allows us to eliminate B, C, D, and E

Answer:

RELATED VIDEO

_________________

Brent Hanneson – GMATPrepNow.com
Image
Sign up for our free Question of the Day emails

Retired Moderator
User avatar
P
Joined: 19 Mar 2014
Posts: 948
Location: India
Concentration: Finance, Entrepreneurship
GPA: 3.5
GMAT ToolKit User Premium Member
Re: If Sally can paint a house in 4 hours, and John can paint  [#permalink]

Show Tags

New post 27 Jun 2017, 14:40
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?

Work Done Together =

\(\frac{ab}{a + b}\)

\(= \frac{4 * 6}{4 + 6}\)

\(= \frac{24}{10}\)

= 2.4 Hrs

= 2 Hours 60 * 0.4 Min

= 2 Hrs 24 Mins


Hence, Answer is A
_________________

"Nothing in this world can take the place of persistence. Talent will not: nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not: the world is full of educated derelicts. Persistence and determination alone are omnipotent."

Best AWA Template: https://gmatclub.com/forum/how-to-get-6-0-awa-my-guide-64327.html#p470475

Manager
Manager
avatar
S
Joined: 14 Jul 2014
Posts: 103
Location: India
Concentration: Social Entrepreneurship, Strategy
GMAT 1: 620 Q41 V34
WE: Information Technology (Computer Software)
If Sally can paint a house in 4 hours, and John can paint  [#permalink]

Show Tags

New post 23 Sep 2018, 10:41
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.

Hence Answer A


Thanks a lot :) I really made a stupid mistake :/


When you have two people (or machines, or other entities) working together to complete a job, you can add their rates together to find their combined rate. Typically, as you see here, the information you are given will be in terms of time. To add the rates, you'll want to first convert times to rates.
GMAT Club Bot
If Sally can paint a house in 4 hours, and John can paint &nbs [#permalink] 23 Sep 2018, 10:41
Display posts from previous: Sort by

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

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


Copyright

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