frekin math problem

Discussion in 'Films, TV, Music, Books, Etc.' started by piracer, Jan 16, 2011.

  1. piracer

    piracer Rookie

    Joined:
    Oct 21, 2002
    Messages:
    4,042
    Likes Received:
    0
    So i know some of you here are pretty good in math, help me out please:

    at a high-school cross-country meet, jarryd jogs 8 mph for the first part of the race, then increased his speed to 12 mph for the second part. If the race was 21 mi long and Jared finished in 2 hr, how far did he jog at the faster pace?

    any help would be great, kthks.
     
    #1
  2. schimmel

    schimmel Rookie

    Joined:
    Nov 8, 2005
    Messages:
    3,231
    Likes Received:
    0
    I'm not gonna solve it for you but think of it this way, when he's running 12 mph every 20 minutes he has traveled 4 miles. If he finishes in 2 hours, then he must have at least spent an entire hour running at 12 mph. Hope that helps.
     
    #2
  3. keepithowitis

    keepithowitis Rookie

    Joined:
    Dec 30, 2007
    Messages:
    3,253
    Likes Received:
    0
    I solved it like this: (answer is in white in case anybody else is trying to solve it)

    If he traveled 1 hour at each speed, he would have traveled 20 miles total (8+12mph). Therefore he traveled a little longer at 12 mph than he did at 8 mph. you could also say that he goes 1 mile every 7.5 minutes at 8 miles an hour, and every 5 minutes at 12 miles an hour. In terms of an equation, it would be 7.5x + 5y = 120. Schimmel was right in saying that at least half of the race must have been at 12 mph, so we can change the equation to 7.5x + 5y = 60 (knowing that half of the race was already run at 12mph). After a little guessing and checking, I determined that he ran 1 hr 15 minutes at 12 mph, and 45 minutes at 8 mph. You can check this through the equation (miles run @ 8mph * minutes/mile @ 8mph) + (miles run @ 12mph * minutes/mile @ 12mph) = (total minutes ran), or (6 * 7.5) + (15 * 5) = 120.
     
    #3
  4. DocMoc

    DocMoc Rookie

    Joined:
    Nov 18, 2005
    Messages:
    1,998
    Likes Received:
    0
    Break up the problem into two parts: the distance he jogged at 8mph and the distance he jogged at 12mph. Breaking it up and looking at them separately will give you two linear velocity questions which you can solve.
     
    #4
  5. piracer

    piracer Rookie

    Joined:
    Oct 21, 2002
    Messages:
    4,042
    Likes Received:
    0
    Sorry, but wouldn't that be a kind of a logic reasoning to get to that? Thing im worried about is that it should follow some form of D=Rt as a uniform motion exercise as the text book says
     
    #5
  6. Lien

    Lien Rookie

    Joined:
    Feb 1, 2008
    Messages:
    3,720
    Likes Received:
    0
    [​IMG]
    Find an answer like that and I'll give you 5 bucks... What? I hate math so much i want it to be destroyed.
     
    #6
  7. Bretimus_v2

    Bretimus_v2 Hey kiddo!

    Joined:
    Jan 30, 2009
    Messages:
    10,979
    Likes Received:
    14
    @piracer. It's still based off of d = rt. But you're extending d=rt a little into d = rt + r't' [the ' denotes a different set of rate and time]. And if there is a fixed total time like this, then T = t + t' (or 2 = t + t'), which can be rearranged into t' = 2 - t. Substitution. d = rt + r'(2-t). Algebra...it makes life simpler... Hope that makes sense.
     
    #7
  8. MattAY

    MattAY Forum Moderator
    Staff Member

    Joined:
    Mar 2, 2006
    Messages:
    13,751
    Likes Received:
    41
    I've gone cross-eyed.

    Cant we just discuss boobs like NORMAL people?
     
    #8
  9. Longo_2_guns

    Longo_2_guns Forum Moderator
    Staff Member

    Joined:
    Jun 29, 2003
    Messages:
    17,189
    Likes Received:
    47
    Boobs are nice.
     
    #9
  10. MattAY

    MattAY Forum Moderator
    Staff Member

    Joined:
    Mar 2, 2006
    Messages:
    13,751
    Likes Received:
    41
    Yeah, they're really nice. I've got a math problem:

    1 boob + 1 boob = ???
     
    #10
  11. Longo_2_guns

    Longo_2_guns Forum Moderator
    Staff Member

    Joined:
    Jun 29, 2003
    Messages:
    17,189
    Likes Received:
    47
    Not enough boobs.
     
    #11
  12. UghRochester

    UghRochester https://www.twitch.tv/ughrochester

    Joined:
    Jun 5, 2006
    Messages:
    8,447
    Likes Received:
    10
    Fix'd
     
    #12
  13. MattAY

    MattAY Forum Moderator
    Staff Member

    Joined:
    Mar 2, 2006
    Messages:
    13,751
    Likes Received:
    41
    Im afraid Longo was right Ugh.

    You should've revised.
     
    #13
  14. Icepick

    Icepick Rookie

    Joined:
    Dec 14, 2002
    Messages:
    11,255
    Likes Received:
    0
    This topic was a lot more interesting when I thought the title was meth problems, 8 years here and everyones still doing their schoolwork together
     
    #14
  15. De-Ting

    De-Ting Rookie

    Joined:
    Nov 11, 2006
    Messages:
    9,058
    Likes Received:
    0
    ITT: Icepick has problems with people continuing their education.
     
    #15
  16. Icepick

    Icepick Rookie

    Joined:
    Dec 14, 2002
    Messages:
    11,255
    Likes Received:
    0
    ITT education is spread by relying on others, thus failing to educate
     
    #16
  17. Longo_2_guns

    Longo_2_guns Forum Moderator
    Staff Member

    Joined:
    Jun 29, 2003
    Messages:
    17,189
    Likes Received:
    47
    Mattay is right about me being right.
     
    #17
  18. piracer

    piracer Rookie

    Joined:
    Oct 21, 2002
    Messages:
    4,042
    Likes Received:
    0
    Erm well i can come to an answer that 45min was done at 8mph and the rest at 12mph (since that totals up nicely). the issue is i still don't quite know how to flesh that out as a formula and not just magically jot those numbers down
     
    #18
  19. Bretimus_v2

    Bretimus_v2 Hey kiddo!

    Joined:
    Jan 30, 2009
    Messages:
    10,979
    Likes Received:
    14
    see my earlier post then
     
    #19
  20. keepithowitis

    keepithowitis Rookie

    Joined:
    Dec 30, 2007
    Messages:
    3,253
    Likes Received:
    0
    See my damn post!!!! I had the whole answer and a formula jeez
     
    #20

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice