Results 1 to 6 of 6

Math Help - Quadratic function word problems

  1. #1
    Junior Member
    Joined
    Sep 2008
    Posts
    71

    Quadratic function word problems

    Hey guys, I have a word problem I'm confused/ stuck on.

    A video game company is selling a new console, the sales of the the system will follow the quadratic function y = -1/50x^2+7x-200.

    1. After how many days is the company going to make a profit?

    2. After how many days do they reach their peak sales?

    3. How many days can they expect to be making a profit on this product?

    4. What is a reasonable domain and range for this?

    So I started out with -b/2a. I got 175 and plugged it into the equation and ended up with 412.5.
    I'm confused because I don't know if I found the answer to # 1 or # 2. I'm guessing I got the maximum for # 2, but what would I find for number 1?

    And the rest I have no clue on what to do.

    Sorry if this sounds confusing.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member rtblue's Avatar
    Joined
    Mar 2009
    From
    Birmingham, Alabama.
    Posts
    221
    For number one, i suggest setting the equation equal to zero, and then solving using the quadratic formula. You know that since 0 is no profit, the value that equals zero is when they will have no money. So they will make money at whatever value is greater than the answer you solved for. And you are right, 412.5 is the maximum profit, and if x is in days, this is made after 175 days.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Sep 2008
    Posts
    71
    Thank you so much! But I find both # 1 and # 3 to be asking the same thing? Can you explain to me what those two are asking?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member rtblue's Avatar
    Joined
    Mar 2009
    From
    Birmingham, Alabama.
    Posts
    221
    Number 1 asks how long it will take the company to make a profit.

    Number 3 asks how long the company will CONTINUE to make a profit.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by Jubbly View Post
    Thank you so much! But I find both # 1 and # 3 to be asking the same thing? Can you explain to me what those two are asking?
    Number 3 is asking the length of time it will remain in profit whereas 1 asks how long it takes to get an initial profit.

    This will be the period between the two solutions given by the quadratic formula
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,987
    Thanks
    1650
    The graph of this quadratic function is a parabola with vertex upward. There will be a time, from 0 to t_0 days, say, while the graph is below the axis, then a time, from t_0 to t_1, say, when it is above the axis, then it goes back down.

    "1) After how many days is the company going to make a profit?"
    is answered by t_0, the time from t= 0 until the graph is above the axis.

    "3) How many days can they expect to be making a profit on this product?"
    is answered by t_1- t_0, the time in days that the graph is above the axis.

    "So I started out with -b/2a. I got 175 and plugged it into the equation and ended up with 412.5. "
    Can you say why you did those things? There is no point in using a formula if you don't know what the formula is for!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Quadratic function word problems
    Posted in the Algebra Forum
    Replies: 6
    Last Post: December 1st 2010, 09:52 AM
  2. help with quadratic word problems?
    Posted in the Pre-Calculus Forum
    Replies: 7
    Last Post: December 9th 2009, 06:01 PM
  3. Quadratic Word Problems
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: October 29th 2009, 03:27 PM
  4. Quadratic word problems
    Posted in the Algebra Forum
    Replies: 1
    Last Post: September 23rd 2007, 11:09 AM
  5. Quadratic Word Problems
    Posted in the Algebra Forum
    Replies: 5
    Last Post: September 23rd 2007, 08:43 AM

Search Tags


/mathhelpforum @mathhelpforum