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December 19, 2014

December 19, 2014

Posted by **kayla** on Friday, September 26, 2008 at 10:27pm.

I know that the expression for nickles would be 5x, for dimes it would be

10x + 40, but i dont understand how to do the expression for quarters.....can someone help me with the answer

- pre calc -
**Quidditch**, Friday, September 26, 2008 at 11:50pmN = number of nickles

D = number of dimes = N+4

Q = number of quarters

= 25-N-D

= 25-N-(N+4)

= 21-(2N)

Add the coins to get $3.20

(N*$0.05) + (D*$0.10) + (Q*$0.25) = $3.20

Expressing D and Q in terms of N:

(N*$0.05) + ((N+4)*$0.10) + (21-2N)*$0.25=$3.20

Solve for N. Then plug N into the equations for D and Q

- pre calc -
**drwls**, Saturday, September 27, 2008 at 12:00amIt is not clear what your x means, and where you came up with 10x + 40 for the value of the dimes. Let the numbers of nickels, dimes and quarters be N, D and Q.

5 N + 10 D + 25 Q = 320

D = N + 4

N + D + Q = 25

Now solve those three equations in three unknowns.

5 N + 10(N + 4) + 25 Q = 320

15 N + 25 Q = 280

2 N + 4 + Q = 25

Multiply that last equation by 25

50 N + 25 Q = 525

Now eliminate the Q

35 N = 245

N = 7

You do the rest

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