Gretchen's local ice cream shop offers 100 different flavors.  She was able to try a 1/4 of the flavors 2 years ago and double that amount last year.  How many more flavors will she need to try this year to have tried all 100 flavors?
The shop offers 100 flavors and she tried 1/4 of the flavors so she had 100*.25 = <<100*.25=25>>25 flavors 2 years ago
Last year she ate double the amount from the previous year so she had 25*2 = <<25*2=50>>50 flavors
2 years ago she ate 25 flavors and last year she had 50 flavors so she has had 25+50 = <<25+50=75>>75 flavors
The shop offers 100 flavors and she has had 75 flavors so she still needs to try 100-75 = <<100-75=25>>25 flavors
#### 25