Linear Algebra

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Rosa ordered 120 pieces of jewelry. a number of bracelets for $10 each a number of necklaces for $12 each. She wrote check for $1400. How many bracelets and necklaces did she buy?

  • Linear Algebra -

    Let
    x=number of bracelets
    y=number of necklaces
    then
    x+y=120
    10x+12y=1400

    Solve for x and y.

    Quick mental calculation, no paper required:
    If Rosa bought only necklaces, she would have paid 12*120=$1440.
    Exchanging a necklace for a bracelet saves her $2, so to pay $1400, she must have saved $40, or bought 20 bracelets and 100 necklaces.

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