SOLUTION: There are 223 coins total of quarters, dimes, and nickels. The total value of the coins is $20.10. How many coins do I have of each?

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Question 517095: There are 223 coins total of quarters, dimes, and nickels. The total value of the coins is $20.10. How many coins do I have of each?

Found 2 solutions by josmiceli, JBarnum:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let q = number of quarters
Let +d+ = number of dimes
Let +n+ = number of nickels
given:
(1) +q+%2B+d+%2B+n+=+223+
(2) +25q+%2B+10d+%2B+5n+=+2010+ ( in cents )
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Multiply both sides of (1) by 5
and subtract (1) from (2)
(2) +25q+%2B+10d+%2B+5n+=+2010+
(1) +-5q+-+5d+-+5n+=+-1115+
+20q+%2B+5d+=+895+
+5d+=+895+-+20q+
+d+=+179+-+4q+
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Suppose there are 100 dimes
+100+=+179+-+4q+
+4q+=+79+ ( doesn't work, d has to be odd)
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107 dimes:
+107+=+179+-+4q+
+4q+=+72+
+q+=+18+
+107+%2B+18+%2B+n+=+223+
+n+=+98+
+25%2A18+%2B+10%2A107+%2B+5%2A98+=+450+%2B+1070+%2B+490+
+2010+
---------
Wow! That was just a guess.
18 quarters, 107 dimes and 98 nickels

Answer by JBarnum(2146) About Me  (Show Source):
You can put this solution on YOUR website!
223=Q%2BD%2BN where QDN = amount of each coin
a quarter is .25 dime .10 nickel .05
20.10=.25Q%2B.10D%2B.05N
oh boy elimination and substitution fun
20.10=.25Q%2B.1D%2B.05N
.1%28223%29=.1%28Q%2BD%2BN%29
-22.3=.1Q%2B.1D%2B.1N%29
subtrct to eliminate dimes
42.40=.15Q-.5N
.
the prob above is that i dont have a 3rd equation and cant do much without one, like if they said there was 100 more dimes than nickels then id have a third equation and could solve this better(d=100+n).
.
yeh im gonna do guess n check
im sure someone can do all that math but guess n check works to:
right off bat 80 quarters is $20 so you know there will be very few quarters
200 dimes is $20 so there will be alot of dimes
so i started by taking 50 from the dimes to make 150 coins then 70 nickles to make 220 coins and then started swaping coins around to stay in the 220s till i got the right combo, i tried to keep the total at a constant 20.10 and realized i either needed 1 extra dime or 2 extra nickels 2 make that 10 cents
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6q=1.50 150d=15 72n=3.60 228=>20.10 nope
8q=2 150d=15 62n=3.10 220=>20.10 nope
5q=1.25 157d=15.70 63n=3.15 225=>20.10 nope
5q=1.25 159d=15.90 59n=2.95 223=>20.10 YES
Q=5, D=159, N=59
apparently theres more than 1 solution lol