Answer:
9 quarters
Explanation:
Total cost of money in the coin bank = $3.55
Let the number of dimes be = d
Let the number of quarters be = q
Let the number of nickels be = n
Where:
1 quarter = $0.25
1 dime = $0.1
1 nickel = $0.05
Hence,
0.1(d) + 0.25(q) +0.05(n) = $3.55
In the question, we are told that:
The number of dimes is four less than the number of quarters, mathematically
d = q - 4
The number of nickels is seven more than the number of quarters, mathematically,
n = q + 7
From the question, we are ask to find q
0.1(d) + 0.25(q) +0.05(n) = $3.55
since d = q - 4
n = q + 7
We substitute
0.1(q - 4) +0.25( q )+ 0.05(q + 7) = $3.55
0.1(q - 4) +0.25( q )+ 0.05(q + 7) =$3.55
0.1q - 0.4 +0.25q + 0.05q + 0.35 = $3.55
Collect like terms
0.1q + 0.25q + 0.05q = 3.55 + 0.4 - 0.35
0.4q = 3.6
q = 3.6/0.4
q = 9
Therefore the number of quarters is 9.