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Math Help - help, age word problem.

  1. #1
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    help, age word problem.

    In 5 years, Dad will be three times as old as his daughter Jill will be then. If the sum of their present ages is 50, how old are they now?



    This is the question and this is my answer but it is incorrect.

    3x + x = 50 + 5

    4x = 55

    x = 13 3/4

    Please tell me what i am doing wrong.
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  2. #2
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    Quote Originally Posted by TheomniJoe View Post
    In 5 years, Dad will be three times as old as his daughter Jill will be then. If the sum of their present ages is 50, how old are they now?



    This is the question and this is my answer but it is incorrect.

    3x + x = 50 + 5

    4x = 55

    x = 13 3/4

    Please tell me what i am doing wrong.
    Okay, I modeled the beginning of the question as:

    x + y = 50

    with x = Dad; y = Jill

    In 5 years, Jill will be five years older, which can be expressed as:
    y+5

    At this point in time, Dad will be three times Jill's age, which is:
    3(y+5)

    Here is the tricky part: Both of them have aged 5 years, so when you set up the equation it looks like:

    3(y+5) + (y+5) = 50 + 5 + 5
    4(y+5) = 60
    y+5 = 15
    y=10

    Substitute y back into original equation to find Dad's Age:
    x + 10 = 50
    x = 40

    And the ages work out in 5 years because Jill will be 15 and Dad will be 45:

    45 = 15*3

    Hope this helps.
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  3. #3
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    Quote Originally Posted by TheomniJoe View Post
    In 5 years, Dad will be three times as old as his daughter Jill will be then. If the sum of their present ages is 50, how old are they now?



    This is the question and this is my answer but it is incorrect.

    3x + x = 50 + 5

    4x = 55

    x = 13 3/4

    Please tell me what i am doing wrong.
    Let x denote the age of the daughter today. In 5 years she'll be (x+5) years old.

    The father is (50-x) years old today; in 5 years he'll be (55-x) years old.

    You know that

    55-x=3(x+5)~\implies~55-x=3x-15

    Solve for x. I've got x = 10.
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  4. #4
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    actually your right i just got x = 10 also. I have not done anything in math as difficult as these word problems. The math is not the hard part, the hard part is getting a logical equation based on the question do you folks have any pointers to give? Cause some of them make me wanna by the way thanks for the help.
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