How do I figure out what My GPA would be for just three classes?

I know my overall GPA, but i was wondering how i would calculate it for just 3 classes. These classes are under a specific subject area and i need the GPA for just these three for job purposes. the grades are A, B, and A.How do I figure out what My GPA would be for just three classes?
It's too much trouble to do all of the math. I use the GPA calculator below:


http://www.back2college.com/gpa.htm





If all your classes are 3 credits, you have a 3.67.How do I figure out what My GPA would be for just three classes?
a's are 4, b's are 3...add them then divide by 3......11/3=3.66
go to gpa calculator in the search engine and put your grades in.