A number of nickels and dimes have a total value of \( \$ 1.65 . \) If the number o nickels and dimes were interchanged, the total value would be \( \$ 1.35 \) . How many nickels and how many dimes are there in the original collection?
13 nickels and 7 dimes.
\(0.1 x + 0.05 y = 1.65,0.1 y + 0.05 x = 1.35 \quad : \quad x = 13 , y = 7\)