The percentage increase from $1.50 to $2.25 is 50%.
Steps:
1st- you first need to subtract the difference (increase). You will end up with .75 cents in increase.
2nd- you will then need to divide the increase (.75) by the original number ($1.50). You end up with .50.
3rd- you will then need to multiply the sum (.50) by 100. you end up with 50%
Answer: There is a 50% increase when not in season.
Hope this helps!