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Math story problem with fractions that I am stuck on.

  1. Aug 29, 2012 #1
    A guy spends 1/6 of his life as a boy, 1/8 as a youth, 1/2 as a man and 15 years as a mature adult. I got about 70 by trial and error but I need to know exactly how to solve it.
     
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  3. Aug 29, 2012 #2

    Dick

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    Let the variable L be the length of his life. Add up all of the parts you've got and equate it to L. Now solve for L.
     
  4. Aug 29, 2012 #3
    I do that and get 15.79. That can't be right.
     
  5. Aug 29, 2012 #4

    Dick

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    No, it isn't. Show what you did.
     
  6. Aug 29, 2012 #5
    (1/6)+(1/8)+(1/2)+15
     
  7. Aug 29, 2012 #6

    Dick

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    One sixth of his life is L/6. What's one eighth of his life? What's the total?
     
  8. Aug 29, 2012 #7
    Going by your logic one eighth would be L/8, I'm not sure what the total is..
     
  9. Aug 29, 2012 #8

    Dick

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    The total is his whole life. That's L. What's the sum that is equal to L? You are doing fine so far. Write the sum that is equal to L.
     
  10. Aug 29, 2012 #9
    L/6+L/8+L/2=L
    Like that?
     
  11. Aug 29, 2012 #10

    Dick

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    Close. What about the 15? Where does that go?
     
  12. Aug 29, 2012 #11
    L/6+l/8+l/2+15=l
     
  13. Aug 29, 2012 #12

    Dick

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    Yes! Now can you use algebra to solve for L? It is pretty close to 70.
     
  14. Aug 29, 2012 #13
    thank you!
     
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