Final answer:
Using the given ratio of nickels to dimes (7:11) and the total amount of coins (90), we find that there are 55 dimes in the piggy bank.
Step-by-step explanation:
The ratio of nickels to dimes in a piggy bank is 7:11, and there are a total of 90 nickels and dimes. To find out how many of them are dimes, we need to solve for the two parts of the ratio that sum up to 90. Let's denote the number of nickels as 7x and the number of dimes as 11x, where x is a common multiplier.
The total number of coins is given by the equation:
7x + 11x = 90
Combining like terms, we get:
18x = 90
Dividing both sides by 18 gives us the value for x:
x = 90 ÷ 18
x = 5
Now we know the multiplier for our ratio, we can find the number of dimes as:
Number of dimes = 11 * x = 11 * 5 = 55 dimes