Amy baked 24 cookies on Monday. She then baked 45 cookies on Tuesday. What is the percent increase in the amount of cookies she baked on Tuesday compared to Monday?
To find the percent increase, we need to first find the difference between the two amounts: 45 cookies - 24 cookies = <<45-24=21>>21 cookies
Then we divide the difference by the original amount and multiply by 100% to express the increase as a percentage: 21 cookies / 24 cookies * 100% = 87.5%. Answer: \boxed{87.5}.