Question 1154972: I have 100 coins in my piggy bank, worth a total of $1.72. If the coins in my bank are only pennies and nickels, then how many of each do I have?
Found 3 solutions by ankor@dixie-net.com, Alan3354, greenestamps:
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! let d = no. of dimes
let p = no. of pennies
:
I have 100 coins in my piggy bank,
d + p = 100
worth a total of $1.72.(coins in my bank are only pennies and nickels)
.10d + .01p = 1.72
get rid of the decimals, multiply by 100
10d + p = 172
:
Use elimination, subtract the 1st equation from the above equation
10d + p = 172
d + p = 100
------------------subtractions\ eliminates p, find d
9d + 0 = 72
d = 72/9
d = 8 dimes
then
100 - 8 = 92 pennies
:
:
Check .10(8) = .01(92) = 1.72
Answer by Alan3354(69443)  (Show Source):
You can put this solution on YOUR website! I have 100 coins in my piggy bank, worth a total of $1.72. If the coins in my bank are only pennies and nickels, then how many of each do I have?
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Another tutor did pennies and dimes.
Use that as a guide to do pennies and nickels.
Answer by greenestamps(13209)  (Show Source):
You can put this solution on YOUR website!
...or, if a formal algebraic solution is not required, solve the problem quickly and easily with some logical reasoning and simple mental arithmetic.
If all 100 coins were pennies; the total would be $1.00. The actual total is $1.72, which is $0.72 larger than $1.00.
Now start replacing pennies with nickels. Each time you do that, the number of coins remains 100 while the total value increases by $0.04.
To make the required addition $0.72, the number of times you need to do that is 72/4 = 18.
So there are 18 nickels; the rest (82) are pennies.
CHECK:
18(5)+82(1) = 90+82 = 172
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