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printer A and printer B

This topic has 1 expert reply and 5 member replies
printer A and printer B Post Fri Jul 10, 2009 10:45 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    Working together, printer A and printer B would finish the task in 24 minutes. Printer A alone would finish the task in 60 minutes. How many pages does the task contain if printer B prints 5 pages a minute more than printer A ?
    1:600
    2:800
    3:1000
    4:1200
    5:1500


    Help me!

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    Post Fri Jul 10, 2009 11:17 pm
    The answer should be : A

    A+B = x/24 pages/min
    A = x/60 pages/min
    B = (x/60 + 5) pages/min

    x/24 = x/60 + (x/60 + 5)
    x/24 - 2x/60 = 5
    Solve for X , X = 600

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    Post Fri Jul 10, 2009 11:28 pm
    good one.Thanks

    we can calculate,B alone can do in 40 mins


    Now say its 600

    A--10(60)=600

    B---15(40)=600

    Together--25(24)=600

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    Post Sun Jan 02, 2011 5:11 am
    time taken by A & B working together = a*b/(a+b)

    60b/(60+b)=24
    b=40
    b takes 40mins to complete the task

    B in a minute=x/40
    A in a minute=x/60

    x/40-x/60=5

    x=600

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    Post Sun Jan 02, 2011 5:20 am
    nhai2003 wrote:
    Working together, printer A and printer B would finish the task in 24 minutes. Printer A alone would finish the task in 60 minutes. How many pages does the task contain if printer B prints 5 pages a minute more than printer A ?
    1:600
    2:800
    3:1000
    4:1200
    5:1500


    Help me!
    We can plug in the answer choices, which represent the number of pages. The correct answer choice will be divisible by 24 and 60. Eliminate B, C and E.

    Answer choice A: 600 pages

    Combined rate for A+B = w/t = 600/24 = 25 pages per minute.
    Rate for A alone = w/t = 600/60 = 10 pages per minute.
    Rate for B alone = Combined rate - A alone = 25-10 = 15 pages per minute.
    Difference between B and A = 15-10 = 5 pages per minute. Success!

    The correct answer is A.

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    Post Tue Apr 10, 2012 12:13 pm
    Rate Time Distance
    Printer A a/60 60 a (Question then becomes what is A?)

    Printer B (a/60)+5 (B prints 5 pages a minute more than printer A)

    Together = a/60 + (a/60)+5
    = a/60 + (a/60) + (300/60) (Same as 5)
    = a/60 + (300 + a)/60 (Add them now as they have a common denominator)
    = (2a + 300)/60 (Combined Rate)
    = a/(2a + 300)/60 = 24 (This is how we got 24;By dividing the distance/combined rate)
    = 60a = 24(2a +300) (Algebra, be careful here!!)
    = 60a - 48a= 24(300) (Do not simplify until the very end:You just waste time by doing so)
    = a= 600
    I think this is faster!

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    Post Tue Apr 10, 2012 9:24 pm
    nhai2003 wrote:
    Working together, printer A and printer B would finish the task in 24 minutes. Printer A alone would finish the task in 60 minutes. How many pages does the task contain if printer B prints 5 pages a minute more than printer A ?
    1:600
    2:800
    3:1000
    4:1200
    5:1500


    Help me!
    AO must be multiple of 60. (bcoz d combined time taken is a whole number)

    Lets start with 600 (on actual GMAT its better to start with B or D rather than starting with extremes A or D)

    A= 600/60 = 10 units of work
    B= 10+ 5= 15 units of work

    combined units of work done in a minute = 25 (10+15 A+B)
    Combined Time taken = total work/combined rate = 600/25 = 24 which is given in the question. Hence AO= A.

    GMAT Quant tip on work rate:
    Always assume the work done as LCM of the individual rates.
    Benefits:
    1. Avoid fractions in calculations and hence avoid calculation mistakes.
    2. Saves few seconds. (do not undermine the few seconds saved on EACH Question)

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