The percentage increase is given by 2.00/0.64*100 or 200/64*100=312.5%, take away 100%=212.5%. (100% represents the original 64 cents.) To avoid decimals in the division you can convert to cents: $2 = 200 cents.
Or take the difference between 64 cents and $2=$1.36 or 136 cents. So 136/64 is the percentage increase in terms of the difference: 136/64*100=212.5%.