2. If Sally can paint a house in 4 hours, and John can paint the same house in 6 hour, how long will it take..?

2. 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?

A. 2 hours and 24 minutes

B. 3 hours and 12 minutes

C. 3 hours and 44 minutes

D. 4 hours and 10 minutes

E. 4 hours and 33 minutes

I know the answer, but I don't understand how it is found so please show the work too. thanks

4 Answers

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  • 10 years ago
    Favorite Answer

    Sally does 1/4 of the work in 1 hour, and John does 1/6 in an hour. In x hours, Sally does x/4 of the work, and John does x/6 of the work.

    x/4 + x/6 = 1 house in x hours

    3x/12 + 2x/12 = 12/12

    5x = 12

    x = 12/5 = 2 2/5 hours

    1/5th of an hour is 60/5 = 12 minutes, so 2/5ths is 24 minutes.

    The answer is 2 hours and 24 minutes.

    Hope that helped.

  • Bill
    Lv 7
    10 years ago

    It takes Sally 4 hours, so she paints 1/4 of the house per hour.

    John paints 1/6 of the house per hour.

    Turn that into 12ths so you can compare and you get Sally painting 3/12 per hour, and John 2/12 per hour. So together they paint 5/12ths per hour.

    That means it takes them 2 hours to paint 10/12ths of the house. Now you just have to figure out how long it takes them to paint the last 2/12ths. Since they do 5/12ths per hour, it takes 2/5ths of an hour to do 2/12ths of the house.

    1/5th of an hour is 12 minutes. So 2/5ths is 24 minutes. Thus 2hrs and 24 min to paint the house.

  • 10 years ago

    every hour Sally can paint 1/4 of the house and John can paint 1/6

    try and work it from there

  • 10 years ago

    I would just kick John out and have Sally do it. She's obviously better at it.

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