SOLUTION: A collection of 42 coins consisting of dimes, quarters, and half-dollars has a value of $11.10. There are two times as many quarters as dimes. Find the number of each kind of coin.

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Question 401466: A collection of 42 coins consisting of dimes, quarters, and half-dollars has a value of $11.10. There are two times as many quarters as dimes. Find the number of each kind of coin.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
d = number of dimes
q = number of quarters
h = number of half-dollars
given:
(1) 10d+%2B+25q+%2B+50h+=+1110 (in cents)
(2) d+%2B+q+%2B+h+=+42
(3) q+=+2d
There are 3 equation and 3 unknowns, so it's solvable
--------------------
Substitute (3) into (1):
(1) 10d+%2B+25%2A%282d%29+%2B+50h+=+1110
(1) 10d+%2B+50d+%2B+50h+=+1110
(1) 6d+%2B+5h+=+111
and
(2) d+%2B+2d+%2B+h+=+42
(2) 3d+%2B+h+=+42
Multiply both sides by 2 and subtract from (1)
(1) 6d+%2B+5h+=+111
(2) -6d+-+2h+=+-84
3h+=+27
h+=+9
and, from (2):
3d+%2B+9+=+42
3d+=+33
d+=+11
from (3):
q+=+2%2A11
q+=+22
There are 11 dimes, 22 quarters, and 9 half dollars
check answer:
(1) 10d+%2B+25q+%2B+50h+=+1110
10%2A11+%2B+25%2A22+%2B+50%2A9+=+1110
110+%2B+550+%2B+450+=+1110
1110+=+1110
OK