Question 345680
A change machine contains nickels, dimes, and quarters.
 There are 75 coins in the machine and the value of the coins is $7.25.
 If there are 5 times as many nickels as dimes,
 find the number of coins of each type in the machine.
;
Write an equation for each statement:
:
"There are 75 coins in the machine"
n + d + q = 75
:
"the value of the coins is $7.25."
.05 + .10d + .25q = 7.25
:
"there are 5 times as many nickels as dimes"
n = 5d
Arrange in the same form
n - 5d = 0
:
Using the coefficients of these 3 equations, write a matrix
(in the 3rd equation q=0
:
1, 1, 1, 75
.05, .10, .25, 7.25
1 - 5, 0, 0 
:
Solve this 3 by 4 matrix using your favorite method
:
My favorite is the matrix feature on the Ti83, I got
n = 50
d = 10
q = 15