How many coins are there?

samedi 28 septembre 2013

1. There are 100 coins on the table. The coins consist of nickels, dimes, and quarters. The total value is $15.85. How many of each coins are there?







3.



I setup a system of equations.

x = nickels

y = dimes

z = quarters



x + y + z = 100

0.05x + 0.10y + 0.25z = 15.85





I then solve and reduce and get:



x + y + z = 100

y + 5z = 217



I move over variables and get:



x = 100 - y - z

y = 217 - 5z



Since there are more variables than equations I assume that there are many solutions, and try using a parametric representation.





x = 100 - y - z

y = 217 - 5t



where t = any real number



I plug in numbers but end up not getting the value 15.85. The most I can get is somewhere near 14.00.



I was wondering if my setup is wrong.

Is there another way to solve this problem?






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