As coins, they are already in their simplest ratio, since 25 and 38 don't have any common factor to divide by. (1 doesn't really count...)
As money, you need to multiply the 25 nickels x 5 cents per nickel, which gives you 125 cents,
and 38 dimes x 10 cents per dime, which gives you 380 cents.
So your new ratio is 125:380, which you can simplify by dividing each by 5, which gives you
SO, as money the ratio in simplest terms is 25:76. As numbers of coins, it's 25:38
If you think about it, it makes sense because:
10 cents is twice as much as 5 cents, and
76 cents is twice as much as 38 cents.
Hope this helps!
Matt in New York