It is currently 19 Sep 2019, 21:20

### 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

# Machine A can produce

Author Message
TAGS:
Founder
Joined: 18 Apr 2015
Posts: 8139
Followers: 157

Kudos [?]: 1710 [1] , given: 7485

Machine A can produce [#permalink]  10 Sep 2019, 12:20
1
KUDOS
Expert's post
00:00

Question Stats:

100% (01:30) correct 0% (00:00) wrong based on 5 sessions
Machine A can produce $$\frac{1}{6}$$ of a ton of paintbrushes in one hour. Machine B can produce $$\frac{1}{14}$$ of a ton of paintbrushes in one hour. Working together at their individual rates, how long would it take the two machines to produce 2 tons of paintbrushes?

A. 8 hours

B. 8 hours 24 minutes

C. 9 hours

D. 9 hours 46 minutes

E. 12 hours

Kudos for the right answer and explanation
[Reveal] Spoiler: OA

_________________

Last edited by Carcass on 10 Sep 2019, 21:32, edited 1 time in total.
Fixed typo
GRE Instructor
Joined: 10 Apr 2015
Posts: 2387
Followers: 78

Kudos [?]: 2358 [1] , given: 33

Re: Machine A can produce [#permalink]  11 Sep 2019, 04:58
1
KUDOS
Expert's post
Carcass wrote:
Machine A can produce $$\frac{1}{6}$$ of a ton of paintbrushes in one hour. Machine B can produce $$\frac{1}{14}$$ of a ton of paintbrushes in one hour. Working together at their individual rates, how long would it take the two machines to produce 2 tons of paintbrushes?

A. 8 hours

B. 8 hours 24 minutes

C. 9 hours

D. 9 hours 46 minutes

E. 12 hours

Kudos for the right answer and explanation

Their COMBINED rate = 1/6 + 1/14 = 7/42 + 3/42 = 10/42 = 5/21 tons per hour

We want to make 2 tons

Time = output/rate
= 2/(5/21)
= (2)(21/5)
= 42/5
= 8 2/5 hours
= 8 hours 24 minutes

Cheers,
Brent
_________________

Brent Hanneson – Creator of greenlighttestprep.com

Manager
Joined: 22 Aug 2019
Posts: 61
Followers: 0

Kudos [?]: 32 [0], given: 8

Re: Machine A can produce [#permalink]  11 Sep 2019, 10:44
Carcass wrote:
Machine A can produce $$\frac{1}{6}$$ of a ton of paintbrushes in one hour. Machine B can produce $$\frac{1}{14}$$ of a ton of paintbrushes in one hour. Working together at their individual rates, how long would it take the two machines to produce 2 tons of paintbrushes?

A. 8 hours

B. 8 hours 24 minutes

C. 9 hours

D. 9 hours 46 minutes

E. 12 hours

Kudos for the right answer and explanation

1 ton / 6 hours and 1 ton/ 14 hours. How fast do these work together? The sum of their rates.

1 / 6 + 1 / 14

= 1/(2*3) + 1/(2*7)
= 7/(2*3*7) + 3/(2*3*7)
= 10 / (2*3*7)
= 5 / (3*7)
= 5 tons / 21 hours

21 hours / 5 tons

4.2 hours per 1 ton

so 8.4 hours for 2 tons.

B.
Re: Machine A can produce   [#permalink] 11 Sep 2019, 10:44
Display posts from previous: Sort by