SOLUTION: A pile of 55 coins consisting of nickels and dimes is worth $3.90 . Find the number of each.

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Question 1042922: A pile of 55 coins consisting of nickels and dimes is worth $3.90 . Find the number of each.
Found 2 solutions by Fombitz, rothauserc:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
1.N%2BD=55
and
5N%2B10D=390
2.N%2B2D=78
Subtract eq. 1 from eq. 2,
N%2B2D-N-D=78-55
D=23
Now use eq. 1, to solve for D.
N%2B23=55

Answer by rothauserc(4718) About Me  (Show Source):
You can put this solution on YOUR website!
let x be the number of nickels and y be the number of dimes
:
we have the following two equations in two unknowns
:
1) x + y = 55
2) .05x + .10y = 3.90
:
solve equation 1) for x and substitute for x in equation 2)
:
x = 55 - y
:
.05(55 - y) + .10y = 3.90
:
2.75 - .05y + .10y = 3.90
:
.05y = 1.15
:
y = 23
x = 32
:
*******************************
we have 32 nickels and 23 dimes
*******************************
:
we check this by substituting for x and y in equation 2)
:
.05(32) + .10(23) = 3.90
:
1.60 + 2.30 = 3.90
:
3.90 = 3.90
:
our answer checks :-)