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Math Help - systems

  1. #1
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    Exclamation systems

    On Friday, the With-IT Clothiers sold some jeans at $25 a pair and some shirts at $18 each. Receipts for the day totaled $441. On Saturday the store priced both items at $20, sold exactly the same number of each item, and had receipts of $420. How many pairs of jeans and how many shirts were sold each day?

    i cant figure this one out, thanks so much! (: (:
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  2. #2
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    The hard part here is taking all this info and making into equations you can work with.

    Let x be the number of jeans sold and y be the number of shirts sold. Then for the first day:

    25x+18y=441

    I just dropped the dollar signs off the prices for convenience. So that means that 25 dollars times the number of jeans sold plus 18 dollars times the number of shirts sold totaled 441 dollars for the day.

    Now for day two. This time, the price of both items is 20 dollars.

    20x+20y=420

    That is done by the same logic as the first equation. Also, we can use the same x and y from the first equation because the problem said the same amount of each item was sold.

    Now you have two equations and two variables and hopefully you can take it from here.
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  3. #3
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    i had that same problem for hw! lol
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  4. #4
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    I got that far..but after that..lol.
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  5. #5
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    Well there are a few ways of going about solving systems. Have you gone over these kind of problems in class? What method have you been using?
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  6. #6
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    uhmm, i think substitution?
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  7. #7
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    Quote Originally Posted by jilly17 View Post
    uhmm, i think substitution?
    Ok, great. So the idea here is to take one of the equations, it doesn't matter which one, and solve it for either x or y. If you solve it for x, you can now substitute all the x's in the other equation with this, and the same thing if you solve for y.

    I'll use the 2nd equation since it's easier to work with.

    20x+20y=420

    x+y=21 (just divided everything by 20)

    x=21-y

    Ok, so we have something here. Take a look at the other original equation.

    25x+18y=441

    Now plug in "21-y" for "x" in this 2nd equation.

    25(21-y)+18y=441

    Now you can solve for y and then use that to solve for x.

    Make sense?
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  8. #8
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    yes! thanks so much! (:
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