Answer:
9 nickels
Explanation:
Changing a quarter to a nickel decreases the value of the sum by $0.20.
When all quarters are changed to nickels and vice versa, the total value will change by the number of excess quarters. That number is ...
($5.95 -3.35)/(0.20) = 2.60/0.20 = 13
The remaining change is made up of equal numbers of nickels and quarters. That amount of change is ...
$5.95 -13ยท0.25 = 2.70
A quarter and nickel together total $0.30, so there must be $2.70/$0.30 = 9 such pairs of coins.
There are 9 nickels and 22 quarters.
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If you don't want to reason through the problem, you can write equations. Let n and q represent the numbers of nickels and quarters, respectively. Then you have ...
0.05n + 0.25q = 5.95
0.25n + 0.05q = 3.35
Multiplying the second equation by 5 and subtracting the first gives ...
5(0.25n +0.05q) -(0.05n +0.25q) = 5(3.35) -(5.95)
1.20n = 10.80
10.80/1.20 = n = 9
The number of nickels is 9.