Page 1 of 2 12 LastLast
Results 1 to 15 of 17
Like Tree1Thanks

Math Help - Algebra and percentages - In need of helpful hints

  1. #1
    Newbie
    Joined
    Jun 2013
    From
    Australia
    Posts
    17

    Algebra and percentages - In need of helpful hints

    Hi everyone, I have a homework question which I don't know how to answer. Here is the question:

    Harry is walking in a marathon. He was intending to complete the marathons total distance of 42km in seven hours while keeping a steady pace of 6km per hour. He was going good for his first four hours but developed a cramp in his legs and stopped to rest for 18 minutes. By what percentage will he need to increase his walking speed for the rest of the marathon if he is still going to complete it in seven hours? Include steps to your answer.

    Now, I'm not sure how to calculate this. I subtracted 18 from the last 3 hours of the marathon and got 2 hours and 42 minutes. I then converted this to a decimal (2.7) and then to a percentage (38.6 2s.f) but I'm not sure I'm on the right track. Another problem is that I'm supposed to incorporate algebra into my answer and I have no idea how to do so. Anybody willing to help me out and confirm whether I'm correct or not on my earlier calculation? Thanks all.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member dokrbb's Avatar
    Joined
    Feb 2013
    From
    ...from out there ;)
    Posts
    236
    Thanks
    21

    Re: Algebra and percentages - In need of helpful hints

    Hi there,

    So, we have the distance he covered during the first 4 hours, find the distance that has to be covered, which you can calculate in meters 42000 - (4*6000) = 42 000 - 24 000 = 18000m

    The speed would be more confortable to be calculated as m/min, which gives you 6km/hr = 6000m/60min = 100m

    He is left with 2hr42 min, or 162min - get now the speed with which he needs to cover those 18000m;

    The percentage you can evaluate in the end, hope this helps,
    Thanks from Crystuls
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jun 2013
    From
    Australia
    Posts
    17

    Re: Algebra and percentages - In need of helpful hints

    Hi there, thanks a lot for your reply! I think I'm beginning to understand a bit better now
    So, I think I figured out the speed by using the calculator: 6.66667km per hour

    Though I should round this to the nearest significant figure: 6.7km per hour. Please feel free to correct me if I am wrong, I need all the help I can get haha. Thanks again!
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    Mar 2013
    From
    Iowa, USA
    Posts
    37
    Thanks
    9

    Re: Algebra and percentages - In need of helpful hints

    looks good, crystuls!
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member dokrbb's Avatar
    Joined
    Feb 2013
    From
    ...from out there ;)
    Posts
    236
    Thanks
    21

    Re: Algebra and percentages - In need of helpful hints

    ...and don't forget to express in percentage the increase you got
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Newbie
    Joined
    Jun 2013
    From
    Australia
    Posts
    17

    Re: Algebra and percentages - In need of helpful hints

    I'm not sure i understand what the speed is (I'm pretty slow, sorry). What is the increase and how do I calculate this to a percentage?

    edit: so was my percentage correct in my first post? The percentage is 38.6%?
    Last edited by Crystuls; June 14th 2013 at 07:19 AM.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Member dokrbb's Avatar
    Joined
    Feb 2013
    From
    ...from out there ;)
    Posts
    236
    Thanks
    21

    Re: Algebra and percentages - In need of helpful hints

    ...but you already have the answer: the initial speed is 6km per hour, for the second part you have got ... 6.7km per hour, isn't it?

    so, what's the increase, and how can it be expressed in %...
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Newbie
    Joined
    Jun 2013
    From
    Australia
    Posts
    17

    Re: Algebra and percentages - In need of helpful hints

    Ah! The increase from 6km/hour to 6.7km/hour is 0.7km, yes? 6 + 0.7 = 6.7
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Member dokrbb's Avatar
    Joined
    Feb 2013
    From
    ...from out there ;)
    Posts
    236
    Thanks
    21

    Re: Algebra and percentages - In need of helpful hints

    yes, and what's the value of 0.7 increase, expressed in percentage?
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Newbie
    Joined
    Jun 2013
    From
    Australia
    Posts
    17

    Re: Algebra and percentages - In need of helpful hints

    70%?
    Follow Math Help Forum on Facebook and Google+

  11. #11
    Member dokrbb's Avatar
    Joined
    Feb 2013
    From
    ...from out there ;)
    Posts
    236
    Thanks
    21

    Re: Algebra and percentages - In need of helpful hints

    Quote Originally Posted by Crystuls View Post
    70%?
    you have 6km/h, which is considered 100%
    and 0.7km/h, which is x %

    how is that 70%???
    Follow Math Help Forum on Facebook and Google+

  12. #12
    Newbie
    Joined
    Jun 2013
    From
    Australia
    Posts
    17

    Re: Algebra and percentages - In need of helpful hints

    Hmm..8.6% (1 s.f) ???

    i got this by: 6 divided by 0.7 = 8.5714 so I just rounded it to 8.6
    Follow Math Help Forum on Facebook and Google+

  13. #13
    Junior Member
    Joined
    Mar 2013
    From
    Iowa, USA
    Posts
    37
    Thanks
    9

    Re: Algebra and percentages - In need of helpful hints

    %  = \frac{.7}{6}(100)
    Follow Math Help Forum on Facebook and Google+

  14. #14
    Member dokrbb's Avatar
    Joined
    Feb 2013
    From
    ...from out there ;)
    Posts
    236
    Thanks
    21

    Re: Algebra and percentages - In need of helpful hints

    Are you sure? ....(0,7 * 100)/6...
    Follow Math Help Forum on Facebook and Google+

  15. #15
    Newbie
    Joined
    Jun 2013
    From
    Australia
    Posts
    17

    Re: Algebra and percentages - In need of helpful hints

    11.7% ?!??!?! I had that calculation earlier when I was focusing on the distance speed time thing but thought it was too big for an increase! WTF!
    Follow Math Help Forum on Facebook and Google+

Page 1 of 2 12 LastLast

Similar Math Help Forum Discussions

  1. Replies: 3
    Last Post: May 11th 2012, 09:34 AM
  2. [SOLVED] Need some hints on this.
    Posted in the Calculus Forum
    Replies: 5
    Last Post: September 17th 2010, 01:45 AM
  3. Need helpful hints
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: December 9th 2009, 07:19 AM
  4. Please give me some hints:
    Posted in the Calculus Forum
    Replies: 5
    Last Post: December 4th 2007, 10:19 AM

Search Tags


/mathhelpforum @mathhelpforum