Anonymous
Anonymous asked in Science & MathematicsMathematics · 6 months ago

One pipe can fill a tank in four hours; another pipe can fill the same tank in three hours.?

How long will it take to fill the tank if both pipes filled it at the same time? Give answer as a fraction

8 Answers

Relevance
  • david
    Lv 7
    6 months ago
    Best Answer

    Rate for 1st = 1/4 tank/hr

    Rate for 2nd = 1/3 tank /hr

    ... mult. each by time to get how much it fills

    ... add to = 1 (need to fill 1 tank)

    (1/4)t + (1/3)t = 1 >>> get common denom.

    3t/12 + 4t/12 = 1

    7t/12 = 1

    t = 12/7 hours

    ======================================

    others did this in different ways, but I am the only one who explained it so you can learn to do more ... this is the BEST ANSWER

    • King Leo
      Lv 7
      6 months agoReport

      I agree with you. You explained well. Good job

  • Como
    Lv 7
    6 months ago

    -

    Let volume of tank be V m³

    Rate for pipe 1 = V/4 m³/h

    Rate for pipe 2 = V/3 m³/h

    Combined rate = 7V/12 m³/h

    Time to fill = V / ( 7V/12) = 12/7 = 1•7 hours = 1 h 42 min

  • Ian H
    Lv 7
    6 months ago

    Add rates in terms of fraction of a tank per hour.

    1/4 + 1/3 = 7/12 of a tank per hour, so takes 12/7 hours to fill 1 tank

  • Mike G
    Lv 7
    6 months ago

    t/4+t/3 = 1

    7t = 12

    t = 12/7 hours

  • How do you think about the answers? You can sign in to vote the answer.
  • 6 months ago

    The first pipe can fill 3 tanks in 12 hours, while the second pipe can fill 4 tanks in 12 hours.

    Together they can fill 7 tanks in 12 hours, which is 1 tank in 12/7 hours.

  • Amy
    Lv 7
    6 months ago

    Least common multiple of 3 and 4 is 12.

    In 12 hours, the first pipe can fill 3 tanks and the second pipe can fill 4 tanks.

    Thus the two pipes together can fill 7 tanks in 12 hours.

    Filling 1 tank takes 12/7 hours.

  • 6 months ago

    Let t hours be the time taken to fill the tank if both pipes filled at the same time.

    The first pipe fills 1/4 of the tank in one hour.

    The second pipe fills 1/3 of the tank in one hour.

    [(1/4) + (1/3)] × t = 1

    [(3/12) + (4/12)] × t = 1

    (7/12)t = 1

    t = 12/7

    t = 1_(5/7)

    It takes 1_(5/7) hours.

  • 6 months ago

    .

    ¼ + ⅓ = 7/12

    time = 1/ (7/12 ) = 12/7 hrs

Still have questions? Get your answers by asking now.