Sam has 18 coins in his pocket that are either quarters or nickels. The total value of these coins is $3.90.

Let q represent the number of quarters and n represent the number of nickels. The following system of equations represents this situation:



How many quarters and nickels does Sam have?

  1. 0
  2. 5
asked by j
  1. Substitute 18-q for n in the second equation and solve for q. Insert that value into the first equation to solve for n. Check by putting both values into the second equation.

    1. 0
    posted by PsyDAG
  2. idk fam

    1. 0
    posted by Anonymous
  3. 9

    1. 0
    posted by Anonymous
  4. what is ittttt I have to do my tenmarksssss

    1. 0
    posted by Anonymous
  5. I too have to do my tenmarks

    1. 0
    posted by Anonymous
  6. Lets first start with what is stated above~

    What we know:
    Q= Quarters
    N= Nickels
    Total amount= $3.90
    Total coins=18

    Q + N= Total coins (18)
    0.25Q(Quarter amount) + 0.05N (Nickel amount)= $3.90 (Total amount)

    Whenever you do problems like this in a systems of equations unit you MUST ALWAYS isolate only 1 letter, leaving only 1 OTHER letter behind as your new equation
    Q + N = 18
    -Q -Q
    New Equation-
    N= 18 - Q

    Your next step is simple, plug and chug (don't discriminate, my teacher taught it to me that way, I remember it better in the weirdest way, as you can see)
    0.25Q + 0.05(insert the N=18 - Q Equation here)= 3.90
    Then simply solve for the equation.

    0.25Q + 0.05(18 - Q)=3.90
    0.9 - 0.05Q=3.90
    Combine like terms
    0.25 + 0.9 - 0.05Q=3.90
    0.2Q + 0.9= 3.90
    -0.9 -0.9

    0.2Q/0.2 = 3/0.2
    Q = 15
    Now for the final step, go back to your N= 18 - Q Equation, and this time, insert your new Q

    N= 18 - Q
    N= 18 - (15)
    N= 3
    Your final results

    This section is for the people who need this equation for homework or for another reason.

    18 coins
    Q= Quarter (0.25)
    N= Nickel (0.05)

    Q + N = 18
    -Q -Q

    0.25Q + + 0.05 N =3.90

    N= 18 - Q

    0.25Q + 0.05(18 - Q)= 3.90

    0.25Q + 0.9 - 0.05Q= 3.90
    0.2Q + 0.9 = 3.90
    -0.9 -0.9

    0.2Q = 3
    _____ _____
    0.2 0.2

    Q = 15

    N= 18 - Q
    N= 18 - (15)
    N= 3

    1. 0
    posted by Ziyada

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