Answer:
25 dimes
Step-by-step explanation:
Given
Coins: Nickels (N), Quarters (Q) , and Dimes (D)
$0.05 = 1 nickel, $0.10 = 1 dime and $0.25 = 1 quarter
So, the amount implies:
[tex]0.05N + 0.10D + 0.25Q = 5.25[/tex]
The number of coin implies:
[tex]N + D + Q = 48[/tex]
and
[tex]N = 7 + Q[/tex]
Required
Determine the number of Dimes
[tex]0.05N + 0.10D + 0.25Q = 5.25[/tex]
[tex]N + D + Q = 48[/tex]
[tex]N = 7 + Q[/tex]
Substitute 7 + Q for N in the first and second equation
[tex]0.05N + 0.10D + 0.25Q = 5.25[/tex]
[tex]0.05(7 + Q) + 0.10D + 0.25Q = 5.25[/tex]
[tex]0.35 + 0.05Q+ 0.10D + 0.25Q = 5.25[/tex]
Collect Like Terms
[tex]0.10D + 0.25Q+0.05Q = 5.25 - 0.35[/tex]
[tex]0.10D + 0.30Q = 4.90[/tex] ----- (1)
[tex]N + D + Q = 48[/tex]
[tex]7 + Q + D + Q = 48[/tex]
Collect Like Terms
[tex]D + Q + Q= 48 - 7[/tex]
[tex]D + 2Q= 41[/tex]
Make Q the subject
[tex]2Q = 41 - D[/tex]
[tex]Q = \frac{41}{2} - \frac{D}{2}[/tex]
[tex]Q = 20.5 - 0.50D[/tex]
Substitute 20.5 - 0.50D for Q in (1)
[tex]0.10D + 0.30Q = 4.90[/tex]
[tex]0.10D + 0.30(20.5 - 0.50D) = 4.90[/tex]
[tex]0.10D + 0.30*20.5 - 0.30*0.50D = 4.90[/tex]
[tex]0.10D + 6.15 - 0.15D = 4.90[/tex]
[tex]0.10D - 0.15D = 4.90 - 6.15[/tex]
[tex]-0.05D = -1.25[/tex]
Solve for D
[tex]D = \frac{-1.25}{-0.05}[/tex]
[tex]D = 25[/tex]
Hence, there are 25 Dimes
