Anonymous
Anonymous asked in Science & MathematicsMathematics · 9 years ago

If Sally can paint a house in 4 hours, and John can paint the same house in 6 hour?

how long will it take for both of them to paint the house together?

4 Answers

Relevance
  • ??????
    Lv 7
    9 years ago
    Favorite Answer

    1/(1/4 + 1/6)

    = 1/((3+2)/12)

    = 12/5

    = 2.4 hours

    = 2 hours 24 minutes

    Reasoning :

    work done 1/4 th house in one hour for Sally

    and 1/6th of the house in one hour for John

    So together they do 1/4 + 1/6 th part of the house in one hour.

    So the time to do the entire house is the inverse of that (1/(1/4+1/6))

  • ?
    Lv 7
    9 years ago

    Sally can paint 1/4 house in 1 hour.

    John can paint 1/6 house in 1 hour.

    So together they can paint (1/4 + 1/6 = 5/12) house in 1 hour.

    Or it will take them 12/5 hr = 2 hr 24 min to paint 1 house.

  • 9 years ago

    2 hours & 24.minutes

  • Phil M
    Lv 7
    9 years ago

    5 hours.

Still have questions? Get your answers by asking now.