SOLUTION: Isabela has $2.55 in quarters,nickels and dimes. She has twice as many nickels as dimes and one less quarter than nickels. How many of each coin does she have?

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Question 1120729: Isabela has $2.55 in quarters,nickels and dimes. She has twice as many nickels as dimes and one less quarter than nickels. How many of each coin does she have?
Found 4 solutions by Shin123, MathTherapy, josgarithmetic, greenestamps:
Answer by Shin123(626) About Me  (Show Source):
You can put this solution on YOUR website!
d=2n
n=q-1
25q%2B5n%2B10d=255 I converted it to cents because we are dealing with cents.
25q%2B5n%2B20n=255
25q%2B25n=255 n=q-1 Add 1 to both sides to get q=n+1
25n%2B5%2B3n=255
28n%2B5=255
28n=250 n= 8 13/14 d=17 6/7 q=9 13/14 Recheck your post.

Answer by MathTherapy(10555) About Me  (Show Source):
You can put this solution on YOUR website!
Isabela has $2.55 in quarters,nickels and dimes. She has twice as many nickels as dimes and one less quarter than nickels. How many of each coin does she have?
There's absolutely NOTHING wrong with your post.
She has:
You can do your own check!
BTW: You just need 1 (ONE) variable to solve for number of each coin. It's a lot easier and you're less prone to making errors!

Answer by josgarithmetic(39625) About Me  (Show Source):
You can put this solution on YOUR website!
system%280.25q%2B0.1d%2B0.05n=2.55%2Cn=2d%2Cn-q=1%29

Look at the last two equations carefully.
system%28d=n%2F2%2Cq=n-1%29
-
simplify the money sum equation.
5q%2B2d%2Bn=51


Substitute for d and q.
5%28n-1%29%2B2%28n%2F2%29%2Bn=51
Find value of n from this equation.
-
5n-5%2Bn%2Bn=51
7n=51%2B5
7n=56
highlight%28n=8%29
and you can find the other two coin counts.

Answer by greenestamps(13203) About Me  (Show Source):
You can put this solution on YOUR website!


Presumably this is a problem from an algebra class, where you are supposed to provide a solution using formal algebra.

But don't underestimate the value of the brain exercise you get by working the problem informally using logical reasoning.

(1) Add one more quarter, so that now the numbers of nickels and quarters are the same; that makes the new total value $2.80.

(2) Now the numbers of quarters and nickels are both twice the number of dimes. So separate the coins into groups of 2 quarters, 2 nickels and 1 dime. The value of each group is then 50+10+10 = 70 cents.

(3) The new total value of the coins is $2.80; the value of each group of coins is 70 cents. That means the number of groups of coins is 280/70 = 4.

(4) So the total number of coins in the 4 groups is 8 quarters, 8 nickels, and 4 dimes.

(5) And last take away that "extra" quarter you added at the beginning. You have the final answer of the $2.55 being made up of 7 quarters, 4 dimes, and 8 nickels.