Results 1 to 4 of 4

Math Help - Don't understand this problem.

  1. #1
    Junior Member Rheanna's Avatar
    Joined
    Nov 2008
    Posts
    36
    Awards
    1

    Don't understand this problem.

    I do kinda of, but for someone reason I doubt I'm getting the answer.

    A cashier has $645 in 10 dollar and 5 dollar bills. There are 90 bills in all. How many of each does the cashier have?


    10x + 5x = 645
    15x=645
    645-90=555

    I know , I know this. but for some reason I can'tfigure it out. lol

    This is just 2 point for extra credit. got the other 14 questions right. Only had to do 8 of 15.

    Thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    12,125
    Thanks
    1009
    A cashier has $645 in 10 dollar and 5 dollar bills. There are 90 bills in all. How many of each does the cashier have?
    let x = number of $10 bills
    y = number of $5 bills

    A cashier has $645 in 10 dollar and 5 dollar bills.

    10x + 5y = 645

    There are 90 bills in all.

    x + y = 90

    solve the system of equations using your favorite method.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Senior Member euclid2's Avatar
    Joined
    May 2008
    From
    Ottawa, Canada
    Posts
    400
    Awards
    1
    Quote Originally Posted by skeeter View Post
    let x = number of $10 bills
    y = number of $5 bills

    A cashier has $645 in 10 dollar and 5 dollar bills.

    10x + 5y = 645

    There are 90 bills in all.

    x + y = 90

    solve the system of equations using your favorite method.
    let x be the amount of 10 dollar bills
    let y be the amount of 5 dollar bills

    (x+y=90)-5
    10x+5y=645
    -5x-5y=-450
    5x=195
    x=39

    sub into original

    39+y=90
    y=90-39
    y=51

    therefore there were 39 10 dollar bills and 51 5 dollar bills
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member Rheanna's Avatar
    Joined
    Nov 2008
    Posts
    36
    Awards
    1
    sorry, I figured it out, once I did the x and y .. before I did it , I was doing x and x, soon as I did x and y I got it. Thank You. I was confusing myself.

    This is way I set it up to figure it out.

    10x + 5 (90-x) = 625

    Then took 90-39 = 51
    Last edited by Rheanna; November 4th 2008 at 07:20 PM.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. How to understand this problem?
    Posted in the Calculus Forum
    Replies: 2
    Last Post: February 20th 2011, 04:17 AM
  2. a problem can't understand it
    Posted in the Algebra Forum
    Replies: 10
    Last Post: August 7th 2010, 09:27 AM
  3. Replies: 0
    Last Post: February 27th 2010, 12:57 PM
  4. I don't understand this problem
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: January 29th 2009, 03:14 PM
  5. Im not sure if i understand this problem :(
    Posted in the Pre-Calculus Forum
    Replies: 15
    Last Post: September 10th 2008, 05:39 PM

Search Tags


/mathhelpforum @mathhelpforum