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grade 9 math!!!!!!!!!! please help

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lavre has sixty-one coins, all of whichare dimes and quaters. if the total value of the coins is $9.85, how many of each kind of coins has she?

  • grade 9 math!!!!!!!!!! please help - ,

    If Q = # quarters
    and D = # dimes.
    Then
    Q+D=61
    .25Q+.10D=9.85
    =================
    Two equations and two unknowns. Solve for Q and D. Check my work.

  • grade 9 math!!!!!!!!!! please help - ,

    Q = 25
    D = 36
    It's a system of linear equations so you can put it into a matrix to solve
    let Matrix A be a 2x2 matrix
    |1 1|
    |.25 .1|
    and have another matrix, B
    |61 |
    |9.85|
    A^-1 * B will give you the answer

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