Anonymous
Anonymous asked in Science & MathematicsMathematics · 1 decade ago

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

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

PS show me the steps...thanks

3 Answers

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  • 1 decade ago
    Favorite Answer

    Do these as rates:

    Sally can paint 1/4 of the house per hour

    John can paint 1/6 of the house per hour

    Working together for T hours, they will complete the whole house.

    (1/4 + 1/6)T = 1

    Get a common denominator of 12:

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

    (5/12)T = 1

    T = 12/5

    T = 2 2/5 hours

    T = 2 hours 24 minutes

    P.S. The shortcut to these rate problems is:

    AB / (A + B)

    A = 4

    B = 6

    4*6 / (4 + 6)

    = 24/10

    = 2.4 hours

    (Remember 0.4 x 60 = 24 minutes)

    Answer:

    A. 2 hours 24 minutes

  • Anonymous
    1 decade ago

    sally paints 1/4 of the house in 1 hour, because in four the whole house is done.

    for the same reason, john paints 1/6 in 1 hour.

    so we add them together.

    1/4 we have to change to 3/12

    and 1/6 to 2/12

    now thats 5/12 for 1 hour with both of them.

    so it would be 10/12 for 2 hours.

    then 2/12 left.

    and don't figure it out, just choose A because it's the only one that is 2 hours. sorry. I'm only 11.

    Source(s): http://answers.yahoo.com/question/index;_ylt=At1qO... this is my question. Please check it out, thx! (it's about asking my parents for an ipod nano)
  • Anonymous
    1 decade ago

    im guessing 3 hours and 44 minutes. I don't know if I'm 100 percent on it though.

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