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Printing press X can print an edition of a newspaper in 12 hours, wher

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Bunuel
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Printing press X can print an edition of a newspaper in 12 hours, wher [#permalink] New post   22 May 2020, 10:19
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Printing press X can print an edition of a newspaper in 12 hours, whereas press Y can print the same edition in 18 hours. What is the total number of hours that it will take the two presses, working together but independently of one another, to print the same edition?

A. 15
B. 7.4
C. 7.2
D. 7.0
E. 6.8


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C
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itachiuchiha
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Re: Printing press X can print an edition of a newspaper in 12 hours, wher [#permalink] New post   25 May 2020, 08:45
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To make the calculations easier, let's take the total work as LCM(12,18) = 36 units of work.

Now, printing press X does = \(\frac{36}{12} = 3\) units of work in an hour

printing press Y does = \(\frac{36}{18} = 2\) units of work in an hour

When both these machines work together then the total amount of work done in an hour = \(3 + 2 = 5\) units of work.

Total hours taken to complete the work = \(\frac{36}{5}\) = 7.2 hours.

IMO, OA - C
Bunuel wrote:
Printing press X can print an edition of a newspaper in 12 hours, whereas press Y can print the same edition in 18 hours. What is the total number of hours that it will take the two presses, working together but independently of one another, to print the same edition?

A. 15
B. 7.4
C. 7.2
D. 7.0
E. 6.8


PS20370
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Re: Printing press X can print an edition of a newspaper in 12 hours, wher [#permalink] New post   22 May 2020, 10:34
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Bunuel wrote:
Printing press X can print an edition of a newspaper in 12 hours, whereas press Y can print the same edition in 18 hours. What is the total number of hours that it will take the two presses, working together but independently of one another, to print the same edition?

A. 15
B. 7.4
C. 7.2
D. 7.0
E. 6.8


PS20370


combined rate = 1/12 + 1/18 ; 10/72
7.2 hrs
OPTION C
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BrentGMATPrepNow
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Re: Printing press X can print an edition of a newspaper in 12 hours, wher [#permalink] New post   22 May 2020, 10:39
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Bunuel wrote:
Printing press X can print an edition of a newspaper in 12 hours, whereas press Y can print the same edition in 18 hours. What is the total number of hours that it will take the two presses, working together but independently of one another, to print the same edition?

A. 15
B. 7.4
C. 7.2
D. 7.0
E. 6.8
PS20370


Let's assign a "nice value" to the job a printing an edition of a newspaper.
We're looking for a number that works well with the given information: 12 hours and 18 hours
Since 36 is the least common multiple of 12 and 18, let's say the job requires the printing presses to print a total of 36 newspapers

Printing press X can print an edition of a newspaper in 12 hours
In other words, printing press X can print 36 newspapers in 12 hours
So, its RATE = 3 newspapers per HOUR

Printing press Y can print an edition of a newspaper in 18 hours
In other words, printing press Y can print 36 newspapers in 18 hours
So, its RATE = 2 newspapers per HOUR

What is the total number of hours that it will take the two presses, working together but independently of one another, to print the same edition?
The combined RATE of the two printing presses = 3 + 2 = 5 newspapers per HOUR

Time = output/rate
So the time to print 36 newspapers = 36/5 = 7.2

Answer: C

Cheers,
Brent
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Re: Printing press X can print an edition of a newspaper in 12 hours, wher [#permalink] New post   24 May 2020, 02:54
C.
Work Rate for X: 1/12
Work Rate for Y: 1/18
Combined Rate: 1/12+1/18 = 5/36
Time: 36/5 = 7.2 hours
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Re: Printing press X can print an edition of a newspaper in 12 hours, wher [#permalink] New post   25 May 2020, 07:17
Rate of X=1/12 job per hr

Rate of X=1/18 job per hr

Combined rate =1/12+1/18=5/36 job per hr

Now we know T=W/R=36/5=7.2 hrs
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Re: Printing press X can print an edition of a newspaper in 12 hours, wher [#permalink] New post   31 Aug 2021, 02:43
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Solution



Given
• Printing press X can print an edition of a newspaper in 12 hours
• Press Y can print the same edition in 18 hours
To find
• The total number of hours that it will take the two presses, working together but independently of one another, to print the same edition

Approach and Working out
• Printing Press X
    o 12 hours -- 1 edition
    o 1 hour – 1/12 edition
• Printing Press Y
    o 18 hours -- 1 edition
    o 1 hour – 1/18 edition
• Press X and Y together
    o 1 hour – (1/12) + (1/18) edition
       That is 1 hour – (5/36) edition
       Hence, 1 edition – 36/5 hours = 7.2 hours

Correct Answer: Option C
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Re: Printing press X can print an edition of a newspaper in 12 hours, wher [#permalink] New post   12 Dec 2022, 13:59
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Re: Printing press X can print an edition of a newspaper in 12 hours, wher [#permalink]
12 Dec 2022, 13:59
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