The coins in the stores cash register total $12.50. The cash register contains only nickels, dimes, and quarters. There are twice as many dimes and nickels. There are also twice as many quarters as dimes. How many dimes are in the cash register?

20 dimes

Step-by-step explanation:

We can group the coins into groups that are ...

4 quarters + 2 dimes + 1 nickel

Then each group satisfies the ratio requirements, and the total value of a group is $1.25.

Since the total value in the register is $12.50, there must be 10 such groups, hence 20 dimes.