Results 1 to 10 of 10
Like Tree6Thanks
  • 2 Post By Debsta
  • 1 Post By DenisB
  • 1 Post By DenisB
  • 2 Post By Monoxdifly

Thread: Working Together

  1. #1
    Super Member harpazo's Avatar
    Joined
    Sep 2014
    From
    NYC
    Posts
    995
    Thanks
    42

    Working Together

    Mary Ann can deliver her newspapers in 30 minutes. It takes Ginger 20 minutes to do the same route. How long would it take them to deliver the newspapers if they work together?

    I know that 30 minutes is 1/2 of an hour.
    I also know that 20 minutes is 1/3 of an hour.

    Let x = time for both girls to work together

    My Equation:

    (1/2) + (1/3) = 1/x

    Is this the correct equation?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Oct 2009
    From
    Brisbane
    Posts
    1,189
    Thanks
    429

    Re: Working Together

    Quote Originally Posted by harpazo View Post
    Mary Ann can deliver her newspapers in 30 minutes. It takes Ginger 20 minutes to do the same route. How long would it take them to deliver the newspapers if they work together?

    I know that 30 minutes is 1/2 of an hour.
    I also know that 20 minutes is 1/3 of an hour.

    Let x = time for both girls to work together

    My Equation:

    (1/2) + (1/3) = 1/x

    Is this the correct equation?
    No, for a few reasons:

    1. If you solve this equation you will get x = 6/5. Does that give you the correct answer?? No, because that would mean 1 hour 12min.
    If they are working together they will take less than 20 min (which is how long Ginger can do it on her own).


    2. Look at the units.
    On the LHS, you have hours + hours (which will give hours).
    On the RHS, your "units" are 1/hour.

    If the units are not the same then the expressions can not be equal.

    Have another go at this one.
    Thanks from topsquark and harpazo
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    Joined
    Feb 2015
    From
    Ottawa Ontario
    Posts
    2,209
    Thanks
    488

    Re: Working Together

    Quote Originally Posted by harpazo View Post
    Mary Ann can deliver her newspapers in 30 minutes.
    It takes Ginger 20 minutes to do the same route.
    How long would it take them to deliver the newspapers if they work together?
    Trick:
    Make the job delivering 60 papers; so:
    Mary: 2 papers per min
    Ginger: 3 papers per min
    Combined: 5 papers per min

    Get my drift?
    Thanks from harpazo
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member harpazo's Avatar
    Joined
    Sep 2014
    From
    NYC
    Posts
    995
    Thanks
    42

    Re: Working Together

    Quote Originally Posted by DenisB View Post
    Trick:
    Make the job delivering 60 papers; so:
    Mary: 2 papers per min
    Ginger: 3 papers per min
    Combined: 5 papers per min

    Get my drift?
    So, 60 papers by 5 papers per minutes = 12 minutes.

    Together, they can do the job in 12 minutes.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Super Member harpazo's Avatar
    Joined
    Sep 2014
    From
    NYC
    Posts
    995
    Thanks
    42

    Re: Working Together

    Quote Originally Posted by Debsta View Post
    No, for a few reasons:

    1. If you solve this equation you will get x = 6/5. Does that give you the correct answer?? No, because that would mean 1 hour 12min.
    If they are working together they will take less than 20 min (which is how long Ginger can do it on her own).


    2. Look at the units.
    On the LHS, you have hours + hours (which will give hours).
    On the RHS, your "units" are 1/hour.

    If the units are not the same then the expressions can not be equal.

    Have another go at this one.
    I got 12 minutes for both to complete the job together following DeniB's break down. However, I would like to know what the proper equation is for this question.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    Joined
    Feb 2015
    From
    Ottawa Ontario
    Posts
    2,209
    Thanks
    488

    Re: Working Together

    x = Mary's time, y = Ginger's time

    Together: 1 / (1/x + 1/y) = 1 / (1/30 + 1/20) = 1 / (2/60 + 3/60) = 1 / (5/60) = 60/5 = 12
    Thanks from harpazo
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Super Member harpazo's Avatar
    Joined
    Sep 2014
    From
    NYC
    Posts
    995
    Thanks
    42

    Re: Working Together

    Quote Originally Posted by DenisB View Post
    x = Mary's time, y = Ginger's time

    Together: 1 / (1/x + 1/y) = 1 / (1/30 + 1/20) = 1 / (2/60 + 3/60) = 1 / (5/60) = 60/5 = 12
    Nicely done! Thanks.
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Super Member harpazo's Avatar
    Joined
    Sep 2014
    From
    NYC
    Posts
    995
    Thanks
    42

    Re: Working Together

    Quote Originally Posted by Debsta View Post
    No, for a few reasons:

    1. If you solve this equation you will get x = 6/5. Does that give you the correct answer?? No, because that would mean 1 hour 12min.
    If they are working together they will take less than 20 min (which is how long Ginger can do it on her own).


    2. Look at the units.
    On the LHS, you have hours + hours (which will give hours).
    On the RHS, your "units" are 1/hour.

    If the units are not the same then the expressions can not be equal.

    Have another go at this one.
    1/20 + 1/30 = 1/x

    Let x = the time they work together

    Multiply both sides by 60.

    (3 + 2) = 60/x

    5 = 60/x

    5x = 60

    x = 60/5

    x = 12

    Answer: 12 minutes
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Member
    Joined
    Apr 2018
    From
    Sukoharjo
    Posts
    80
    Thanks
    19

    Re: Working Together

    Quote Originally Posted by harpazo View Post
    So, 60 papers by 5 papers per minutes = 12 minutes.

    Together, they can do the job in 12 minutes.
    Damn, why did I never think of this? I always do it like this:
    Quote Originally Posted by DenisB View Post
    x = Mary's time, y = Ginger's time

    Together: 1 / (1/x + 1/y) = 1 / (1/30 + 1/20) = 1 / (2/60 + 3/60) = 1 / (5/60) = 60/5 = 12
    Thanks from topsquark and harpazo
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Super Member harpazo's Avatar
    Joined
    Sep 2014
    From
    NYC
    Posts
    995
    Thanks
    42

    Re: Working Together

    Thank you everyone.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. working with min{f(x),f(y)}
    Posted in the Calculus Forum
    Replies: 2
    Last Post: Sep 29th 2015, 06:28 PM
  2. tex not working?
    Posted in the LaTeX Help Forum
    Replies: 4
    Last Post: Jan 26th 2015, 11:47 AM
  3. Working Together
    Posted in the Algebra Forum
    Replies: 7
    Last Post: Sep 27th 2014, 09:27 AM
  4. Why isn't this working?
    Posted in the LaTeX Help Forum
    Replies: 2
    Last Post: Oct 23rd 2013, 06:30 PM
  5. Working Alone
    Posted in the Math Topics Forum
    Replies: 5
    Last Post: Jan 11th 2007, 10:35 PM

/mathhelpforum @mathhelpforum