SOLUTION: Carlos has a box of coins that he uses when playing poker with friends. The box currently contains 39 ​coins, consisting of​ pennies, dimes, and quarters. The number of

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Question 1091589: Carlos has a box of coins that he uses when playing poker with friends. The box currently contains 39 ​coins, consisting of​ pennies, dimes, and quarters. The number of pennies is equal to the number of​ dimes, and the total value is ​$3.90. How many of each denomination of coin does he​ have?
Found 3 solutions by jorel1380, MathTherapy, ikleyn:
Answer by jorel1380(3719)   (Show Source): You can put this solution on YOUR website!
Let p be pennies, d be dimes, and q be quarters. The number of pennies is equal to the number of dimes, so p=d. Then:
p+d+q=39
2p+q=39 and
1p+10d+25q=390
1p+10p+25q=390
So:
2p+q=39
11p+25q=390
Then solve for p and q. ☺☺☺☺
Answer by MathTherapy(10556)   (Show Source): You can put this solution on YOUR website!

Carlos has a box of coins that he uses when playing poker with friends. The box currently contains 39 ​coins, consisting of​ pennies, dimes, and quarters. The number of pennies is equal to the number of​ dimes, and the total value is ​$3.90. How many of each denomination of coin does he​ have?
Let number of dimes be D, and quarters, Q

Then number of pennies also = D

We then get: D + D + Q = 39______2D + Q = 39_____Q = 39 - 2D ------ eq (i)

Also, .01D + .1D + .25Q = 3.9_____.11D + .25Q = 3.9_____-eq (ii)

.11D + .25(39 - 2D) = 3.9 ------ Substituting 39 - 2D for Q in eq (ii)

.11D + 9.75 - .5D = 3.9

.11D - .5D = 3.9 - 9.75

- .39D = - 5.85

D, or number of dimes/number of pennies = 

Number of quarters:  

Answer by ikleyn(52871)   (Show Source): You can put this solution on YOUR website!
 .

For coin problems and their detailed solutions see the lessons in this site:



    - Coin problems



    - More Coin problems



    - Solving coin problems without using equations



    - Kevin and Randy Muise have a jar containing coins



    - Typical coin problems from the archive



    - Solving coin problems mentally by grouping without using equations



    - Santa Claus helps solving coin problem





You will find there the lessons for all levels - from introductory to advanced,

and for all methods used - from one equation to two equations and even without equations. 





Read them attentively and become an expert in this field.





Also, you have this free of charge online textbook in ALGEBRA-I in this site



    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.





The referred lessons are the part of this online textbook under the topic "Coin problems".







 

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