1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Tricky precalculus word problem

  1. Feb 9, 2010 #1
    1. The problem statement, all variables and given/known data
    I need to figure out the formula and answer for this word problem.

    it says "A few years ago at her birthday party, mary said take the year it will be 3 decades from now. Subtract the year of my birth and add the year it was one century ago. You now have my birth year.

    however im not trying to find out her birth year but rather what year it was when she was talking about this riddle.

    Basically she is telling people at her birthday party thats taken place a few years ago from the present year this riddle and I need to find out what year it was when she was talking about this riddle.

    2. Relevant equations
    I came up with using X as the variable for the year it was when she was talking about this at her birthday party and Y as her birth year.

    3. The attempt at a solution

    the closest i could come up with is (X-30) - Y + (x-100) = Y

    x-30 is take the year it will be 3 decades ago when she told this riddle

    -Y for subtracting the year of her birth

    then +(X-100) for adding the year it was one century ago when she told this riddle.

    and then = Y for resulting in her birth year.

    So the Y cancel each other out, as im sure it was supposed too since I cant have 2 unknowns if I am to solve this but If I solve for X I get 35 and that doesn't seem too right as it should end up with something like 1995 or something close as the present year is 2010 and in the math problem it states a few years ago is when she talked about this riddle. Any ideas ? thanks for your help

    edit* I just realized the Y doesnt cancel lol well Im out of ideas
  2. jcsd
  3. Feb 9, 2010 #2
    I believe she talks about x+30, not x-30

    However I can only see how old she was when it has all been told.
  4. Feb 9, 2010 #3
    Magwas is correct. Anyway, I checked with a couple of random years, and it would appear that the description given would apply to any year, or at least more than one, so all you can find is her age.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook