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Pipe A runs 30 liters of water per minute into a pool that h

This topic has 2 expert replies and 0 member replies

Pipe A runs 30 liters of water per minute into a pool that h

Post Thu Nov 09, 2017 4:33 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    Pipe A runs 30 liters of water per minute into a pool that has a total volume of 3,600 liters. Pipe B fills a third of the pool in 6 hours.

    Working together how long will it take both pipes to fill the pool?

    A. 2 hours and 36 minutes
    B. 1.5 hours
    C. 9 hours and 12 minutes
    D. 15 hours
    E. 1 hour and 48 minutes.

    OA: E

    Is there a strategic approach to this question?

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    Post Thu Nov 09, 2017 9:18 pm
    ardz24 wrote:
    Pipe A runs 30 liters of water per minute into a pool that has a total volume of 3,600 liters. Pipe B fills a third of the pool in 6 hours.

    Working together how long will it take both pipes to fill the pool?

    A. 2 hours and 36 minutes
    B. 1.5 hours
    C. 9 hours and 12 minutes
    D. 15 hours
    E. 1 hour and 48 minutes.

    OA: E

    Is there a strategic approach to this question?
    For pipe A, at the rate of 30 lit/min, it will take 3600/30 = 120 min = 2 hours, working individually, to fill the pool.
    Since Pipe B fills one-third of the pool in 6 hours, it will take 6*3 = 18 hours, working individually, to fill the pool.

    Working together, both the pipes will fill 1/2 + 1/18 = 5/9 part of the pool in an hour.

    Thus, it will take both the pipes will take 9/5 = 1 hr 48 min. to fill the pool.

    The correct answer: E

    Hope this helps!

    -Jay
    _________________
    Manhattan Review GMAT Prep

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    Thanked by: ardz24
    Post Fri Nov 10, 2017 8:45 am
    ardz24 wrote:
    Pipe A runs 30 liters of water per minute into a pool that has a total volume of 3,600 liters. Pipe B fills a third of the pool in 6 hours.

    Working together how long will it take both pipes to fill the pool?

    A. 2 hours and 36 minutes
    B. 1.5 hours
    C. 9 hours and 12 minutes
    D. 15 hours
    E. 1 hour and 48 minutes.
    Let's determine the COMBINED RATE of the two pipes

    Given: Pipe A's RATE = 30 liters per minute
    This is equivalent to 1800 liters per HOUR

    Pipe B fills a third of the pool in 6 hours
    So, Pipe B fills the ENTIRE pool (3600 liters) in 18 hours
    Rate = Output/time
    = 3600/18
    = 200 liters per hour

    COMBINED RATE = 1800 + 200
    = 2000 liters per hour


    Working together how long will it take both pipes to fill the pool?
    Time = output/rate
    = 3600/2000
    = 36/20 hours
    = 9/5 hours
    = 1 4/5 hours
    = 1 hour and 48 minutes
    = E

    Cheers,
    Brent

    _________________
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    Thanked by: ardz24
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