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Addition And Word Problems

  1. Nov 13, 2005 #1
    5X-5/2Y=-55
    4X+2Y=-12
    USE ADDITION METHOD...HOW I DO THIS PROBLEM THE FRACTIONS THROW ME OFF

    ALSO
    A VENDOR SELLS HOT DOGS AND BAGS OF CHIPS.A CUSTOMER BUYS 2 HOT DOGS AND 2 BAGS OF CHIPS FOR $7.00.ANOTHER CUSTOMER BUYS 4 HOT DOGS AND 5 BAGS OF CHIPS FOR $15.00.FIND THE COST OF EACH ITEM.

    SOLVE:THE ANWSER IS $2.50 HOT DOGS AND CHIPS $1.00.

    4x+3y=$12.25
    2x+5y=$8.75
    IS THAT HOW I SHOULD SET IT UP.THEN WHAT I DO?...SORRY MY NAME GOES PERFECT WITH THIS PROBLEM
     
  2. jcsd
  3. Nov 13, 2005 #2
    You can just solve this by substitution. From the second equation:

    4x+2y=-12
    4x=-2y-12
    2x=-y-6
    y=(-2x-6)

    So, you substitute that value in for y, and you get:

    5x-(5/2)(-2x-6)=-55
    5x-(-5x-15)=55
    5x+5x+15=55
    10x=40
    x=4

    Then, we replace x with 4, which gives us:

    4(4)+2y=-12
    16+12+2y=0
    2y=-28
    y=-14

    So, x=4 and y=-14

    Correct.

    Again, this is called "solving a system of equations". You can use all sorts of methods to solve this, including solvin by substitution (which I used for the first question), elimination (trying to combine the equations, making one variable cancel), and even matricies. I might elaborate in a bit, but I'm getting increasingly sleepy...
     
    Last edited: Nov 13, 2005
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